Question

Solve the system by substitution
-x-y-z=-8
-4x+4y+5z=7
2x+2z=4

Answer 1

"substitute" one equation if for the other (you have to solve for one variable first: this can be done with either the first or last equation)

Answer 2

so can you show me how to do that

Answer 3

-x-y-z = -8
-x = -8 + y +z
x = 8 - y - z
plug (8 - y - z) for x

Answer 4

actually you have to do this kind of thing twice