Question

5. Which might be your first step if you want to solve the

system by elimination?
1st equation: 5x + 4y = 7
2nd equation: 2x - 3y = 3
A) Substitute -10y + 7 for x in the second equation.
B) Substitute 3y + 3 for x in the second equation.
C) Multiply the first equation by 3, multiply the second
equation by 4, then add the resulting equations
together.
D Multiply the first equation by 2, multiply the second
equation 5, then add the resulting equations together.

Answer 1

a is the right answer for you

Answer 2

C)

Explanation:

elimination is not substitution.

therefore, A and B are out.

D does not work, because in the described way the x terms don't get different signs, and the addition does not eliminate any variable.

C brings both y terms to the same absolute value, and their signs are different, so the addition will eliminate the y terms leaving us with one equation in x that we can solve :

15x + 12y = 21

8x - 12y = 12

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23x 0 = 33

23x = 33

x = 33/23