Answer:
5
Step-by-step explanation:
First you would need to add the two equations.
6x + 5y - 2z = -4 + 4x + 5y + 12z = 54
Doing this, you would get:
10x+10y+10z=50
Then, divide all parts of the equation by 10 to isolate the variables.
So,
10x+10y+10z=50/10 =
x+y+z = 5
