For the following system, if you isolated x in the second equation to use the Substitution Method, what expression would you substitute into the first equation?

3x + y = 8
−x − y = −7

A. –y + 7
B. –y − 7
C. y + 7
D. y – 7

Is it D?

Question

For the following system, if you isolated x in the second equation to use the Substitution Method, what expression would you substitute into the first equation?

3x + y = 8
−x − y = −7 

A. –y + 7
B. –y − 7
C. y + 7
D. y – 7

Is it D?

anonymous · Answer

Let's isolate x in the 2nd equation:
-x-y=-7
-x=y-7
divide by -1:
x=-y+7

anonymous · Answer

ohh, so its A. Okay, thanks for the help! :)