Is z = 30 a set solution or all real numbers are solutions?

Question

The equation us 0.3(2z + 7) + 12.3 = 0.6(2z - 6)

Answer 1

.3(2z+7) + 12.3 = .6(2z-6)

.6z +2.1 +12.3 = 1.2z - 3.6

.6z = 14.4 +3.6= 18

z = 180/6= 30

z=30 is the solution set, no other real values