76+8z=100 ;7-22z=7; 15a+15=15

Question

76+8z=100 ;7-22z=7; 15a+15=15

Answer 1

8z=100-76
8z=24
z=3

-22z=7-7
-22z=0
z=0

15a=15-15
15a=0
a=0

Answer 2

76+8z=100
8z=24
z=3
7-22z=7
-22z=0
z=0
15a+15=15
15a=0
a=0