Solve the system by substitution

-x - y - z = - 8

-4x + 4y + 5z = 7

2x + 2z = 4

First:

2x + 2z = 4

2 (x+z) = 4

x+z=4/2

x=2-z

-x - y - z = - 8

- (2-z) - y-z = - 8 replace x

-2+z-y-z = - 8 (cancel z)

-2-y = - 8

6 = y

Then:

-4x + 4y + 5z = 7 replace x and y

-4 (2-z) + 4*6 + 5z = 7

-8 + 4z + 24 + 5z = 7

16 + 9z = 7

9z = 7 - 16

9z = - 9

z = - 9/9

z = - 1

Finally

x = 2-z replace z

x = 2 - (-1)

x = 3