Question

Solve the system by substitution.

-x-y-z=-8
-4x+4y+5z=7
2x+2z=4

Answer 1

the 3rd equation can be written as
z = 2-x
using that in the other two, we have
-x-y-(2-x) = -8
-4x+4y+5(2-x) = 7
rearranged, the top equation is just y = 6
the second now becomes
-4x+24+10-5x = 7
-9x = -27
x = 3
and z = 2-x = -1
so the solution is (3,6,-1)