Evaluate the expression 3b - ac when a = 2. b = 3, and

c=-1.5.

Substituting the given values into the expression, we have:

3b - ac = 3(3) - 2(2)(-1.5)
= 9 - 6(-1.5)
= 9 + 9
= 18

Therefore, the value of the expression 3b - ac when a = 2, b = 3, and c = -1.5 is 18.