Instructions: For questions 1-41, solve the systems of equations by elimination.
1. [latex]\left\{\begin{array}{c}5x+2y=2\\ -3x-y=0\end{array}\right.[/latex]
2. [latex]\left\{\begin{array}{c}-3x+y=-9\\ x-2y=-12\end{array}\right.[/latex]
Solution
[latex](6,9)[/latex]
3. [latex]\left\{\begin{array}{c}6x-5y=-1\\ 2x+y=13\end{array}\right.[/latex]
4. [latex]\left\{\begin{array}{c}3x-y=-7\\ 4x+2y=-6\end{array}\right.[/latex]
Solution
[latex]\left(-2,1\right)[/latex]
5. [latex]\left\{\begin{array}{c}x+y=-1\\ x-y=-5\end{array}\right.[/latex]
6. [latex]\left\{\begin{array}{c}x+y=-8\\ x-y=-6\end{array}\right.[/latex]
Solution
[latex]\left(-7,-1\right)[/latex]
7. [latex]\left\{\begin{array}{c}3x-2y=1\\ -x+2y=9\end{array}\right.[/latex]
8. [latex]\left\{\begin{array}{c}-7x+6y=-10\\ x-6y=22\end{array}\right.[/latex]
Solution
[latex]\left(-2,-4\right)[/latex]
9. [latex]\left\{\begin{array}{c}3x+2y=-3\\ -x-2y=-19\end{array}\right.[/latex]
10. [latex]\left\{\begin{array}{c}5x+2y=1\\ -5x-4y=-7\end{array}\right.[/latex]
Solution
[latex]\left(-1,3\right)[/latex]
11. [latex]\left\{\begin{array}{c}6x+4y=-4\\ -6x-5y=8\end{array}\right.[/latex]
12. [latex]\left\{\begin{array}{c}3x-4y=-11\\ x-2y=-5\end{array}\right.[/latex]
Solution
[latex]\left(-1,2\right)[/latex]
13. [latex]\left\{\begin{array}{c}5x-7y=29\\ x+3y=-3\end{array}\right.[/latex]
14. [latex]\left\{\begin{array}{c}6x-5y=-75\\ -x-2y=-13\end{array}\right.[/latex]
Solution
[latex]\left(-5,9\right)[/latex]
15. [latex]\left\{\begin{array}{c}-x+4y=8\\ 3x+5y=10\end{array}\right.[/latex]
16. [latex]\left\{\begin{array}{c}2x-5y=7\\ 3x-y=17\end{array}\right.[/latex]
Solution
[latex](6,1)[/latex]
17. [latex]\left\{\begin{array}{c}5x-3y=-1\\ 2x-y=2\end{array}\right.[/latex]
18. [latex]\left\{\begin{array}{c}7x+y=-4\\ 13x+3y=4\end{array}\right.[/latex]
Solution
[latex]\left(-2,10\right)[/latex]
19. [latex]\left\{\begin{array}{c}-3x+5y=-13\\ 2x+y=-26\end{array}\right.[/latex]
20. [latex]\left\{\begin{array}{c}3x-5y=-9\\ 5x+2y=16\end{array}\right.[/latex]
Solution
[latex](2,3)[/latex]
21. [latex]\left\{\begin{array}{c}4x-3y=3\\ 2x+5y=-31\end{array}\right.[/latex]
22. [latex]\left\{\begin{array}{c}4x+7y=14\\ -2x+3y=32\end{array}\right.[/latex]
Solution
[latex]\left(-7,6\right)[/latex]
23. [latex]\left\{\begin{array}{c}5x+2y=21\\ 7x-4y=9\end{array}\right.[/latex]
24. [latex]\left\{\begin{array}{c}3x+8y=-3\\ 2x+5y=-3\end{array}\right.[/latex]
Solution
[latex]\left(-9,3\right)[/latex]
25. [latex]\left\{\begin{array}{c}11x+9y=-5\\ 7x+5y=-1\end{array}\right.[/latex]
26. [latex]\left\{\begin{array}{c}3x+8y=67\\ 5x+3y=60\end{array}\right.[/latex]
Solution
[latex](9,5)[/latex]
27. [latex]\left\{\begin{array}{c}2x+9y=-4\\ 3x+13y=-7\end{array}\right.[/latex]
28. [latex]\left\{\begin{array}{c}\frac{1}{3}x-y=-3\\ x+\frac{5}{2}y=2\end{array}\right.[/latex]
Solution
[latex]\left(-3,2\right)[/latex]
29. [latex]\left\{\begin{array}{c}x+\frac{1}{2}y=\frac{3}{2}\\ \frac{1}{5}x-\frac{1}{5}y=3\end{array}\right.[/latex]
30. [latex]\left\{\begin{array}{c}x+\frac{1}{3}y=-1\\ \frac{1}{2}x-\frac{1}{3}y=-2\end{array}\right.[/latex]
Solution
[latex]\left(-2,3\right)[/latex]
31. [latex]\left\{\begin{array}{c}\frac{1}{3}x-y=-3\\ \frac{2}{3}x+\frac{5}{2}y=3\end{array}\right.[/latex]
32. [latex]\left\{\begin{array}{c}2x+y=3\\ 6x+3y=9\end{array}\right.[/latex]
Solution
infinitely many solutions
33. [latex]\left\{\begin{array}{c}x-4y=-1\\ -3x+12y=3\end{array}\right.[/latex]
34. [latex]\left\{\begin{array}{c}-3x-y=8\\ 6x+2y=-16\end{array}\right.[/latex]
Solution
infinitely many solutions
35. [latex]\left\{\begin{array}{c}4x+3y=2\\ 20x+15y=10\end{array}\right.[/latex]
36. [latex]\left\{\begin{array}{c}3x+2y=6\\ -6x-4y=-12\end{array}\right.[/latex]
Solution
infinitely many solutions
37. [latex]\left\{\begin{array}{c}5x-8y=12\\ 10x-16y=20\end{array}\right.[/latex]
38. [latex]\left\{\begin{array}{c}-11x+12y=60\\ -22x+24y=90\end{array}\right.[/latex]
Solution
inconsistent, no solution
39. [latex]\left\{\begin{array}{c}7x-9y=16\\ -21x+27y=-24\end{array}\right.[/latex]
40. [latex]\left\{\begin{array}{c}5x-3y=15\\ y=\frac{5}{3}x-2\end{array}\right.[/latex]
Solution
inconsistent, no solution
41. [latex]\left\{\begin{array}{c}2x+4y=7\\ y=-\frac{1}{2}x-4\end{array}\right.[/latex]
Instructions: For questions 42-49, translate to a system of equations and solve.
42. The sum of two numbers is [latex]65[/latex]. Their difference is [latex]25[/latex]. Find the numbers.
Solution
The numbers are [latex]20[/latex] and [latex]45[/latex].
43. The sum of two numbers is [latex]37[/latex]. Their difference is [latex]9[/latex]. Find the numbers.
44. The sum of two numbers is [latex]-27[/latex]. Their difference is [latex]-59[/latex]. Find the numbers.
Solution
The numbers are [latex]16[/latex] and [latex]-43[/latex].
45. The sum of two numbers is [latex]-45[/latex]. Their difference is [latex]-89[/latex]. Find the numbers.
46. Andrea is buying some new shirts and sweaters. She is able to buy [latex]3[/latex] shirts and [latex]2[/latex] sweaters for [latex]$114[/latex] or she is able to buy [latex]2[/latex] shirts and [latex]4[/latex] sweaters for [latex]$164[/latex]. How much does a shirt cost? How much does a sweater cost?
Solution
A shirt costs [latex]$16[/latex] and a sweater costs [latex]$33[/latex].
47. Peter is buying office supplies. He is able to buy [latex]3[/latex] packages of paper and [latex]4[/latex] staplers for [latex]$40[/latex] or he is able to buy [latex]5[/latex] packages of paper and [latex]6[/latex] staplers for [latex]$62[/latex]. How much does a package of paper cost? How much does a stapler cost?
48. The total amount of sodium in [latex]2[/latex] hot dogs and [latex]3[/latex] cups of cottage cheese is [latex]4720[/latex] mg. The total amount of sodium in [latex]5[/latex] hot dogs and [latex]2[/latex] cups of cottage cheese is [latex]6300[/latex] mg. How much sodium is in a hot dog? How much sodium is in a cup of cottage cheese?
Solution
There are [latex]860[/latex] mg in a hot dog. There are [latex]1\text{,}000[/latex] mg in a cup of cottage cheese.
49. The total number of calories in [latex]2[/latex] hot dogs and [latex]3[/latex] cups of cottage cheese is [latex]960[/latex] calories. The total number of calories in [latex]5[/latex] hot dogs and [latex]2[/latex] cups of cottage cheese is [latex]1190[/latex] calories. How many calories are in a hot dog? How many calories are in a cup of cottage cheese?
Instructions: For questions 50-53, decide whether it would be more convenient to solve the system of equations by substitution or elimination.
50.
a.[latex]\left\{\begin{array}{c}8x-15y=-32\\ 6x+3y=-5\end{array}\right.[/latex]
b.[latex]\left\{\begin{array}{c}x=4y-3\\ 4x-2y=-6\end{array}\right.[/latex]
Solution
a. elimination
b. substitution
51.
a.[latex]\left\{\begin{array}{c}y=7x-5\\ 3x-2y=16\end{array}\right.[/latex]
b.[latex]\left\{\begin{array}{c}12x-5y=-42\\ 3x+7y=-15\end{array}\right.[/latex]
52.
a.[latex]\left\{\begin{array}{c}y=4x+9\\ 5x-2y=-21\end{array}\right.[/latex]
b.[latex]\left\{\begin{array}{c}9x-4y=24\\ 3x+5y=-14\end{array}\right.[/latex]
Solution
a. substitution
b. elimination
53.
a.[latex]\left\{\begin{array}{c}14x-15y=-30\\ 7x+2y=10\end{array}\right.[/latex]
b.[latex]\left\{\begin{array}{c}x=9y-11\\ 2x-7y=-27\end{array}\right.[/latex]