h(x)= 2x+5 and g(x)= 8-3x. What is the value of h(g(1.5))?

I got the h(g)1.5))=7.5 I know its incorrect but need some help on it.

Not sure what steps you took (I can never understand students who say they got something wrong and then don't show how they did it!), but just start off with your expression, and start substituting values, from the inside out:

h(g(1.5)) = h(8-3*1.5) = h(8-4.5) = h(3.5) = 2(3.5)+5 = 7+5 = 12