Answer:
z = -5
Step-by-step explanation:
3(0.7z + 2.8) = 7(1.5z + 7.2)
2.1z + 8.4 = 10.5z + 50.4
2.1z - 10.5z = 50.4 - 8.4
-8.4z = 42
z = 42/(-8.4)