Answer:
C
Step-by-step explanation:
6(a+b) + 2z = -8 ; divide by 2
3(a+b) + z = -4
a+b+z = 2; subtract z from both sides
a+b = 2-z; substitute a+b into equation 3(a+b) +z = -4
3(2-z) +z = -4; distribute
6 - 3z+ z= -4 ; subtract 6 on both sides
-3z + z = -4 -6 ; combine like terms
-2z = -10; divide both sides by -2
z= 5
3(a+b) +z = -4; substitute z by 5
3(a+b) +5 = -4; subtract 5 from both sides
3( a+b) = -4 -5; combine like terms
3(a+b) = -9; divide both sides by 3
(a+b) = -3
