Question

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

2x + y = 9
−x − y = −8

Answer 1

−8 + y

−8 − y

8 + y

8 − y

Answer 2

start with the second equation −x − y = −8 and add y to both sides to get

−x − y = −8

−x − y+y = −8 +y

-x + 0y = -8 + y

-x = -8 + y


Then multiply both sides by -1 to fully isolate x

-x = -8 + y

-1*(-x) = -1*(-8 + y)

x = 8 - y

Answer 3

alternatively, you can do it this way

−x − y = −8

− y = −8 + x

-y + 8 = x

x = -y + 8

x = 8 - y