D(x)=x^2+2x

Question

h(x)=7

h(D)=

Answer 1

As I noted before, I don't like your notation

Does h(D) mean h(D(x)) or (h◦D)(x) ?
Those are standard notation .

Answer 2

I mean h(D(x)). Sorry about that. That's how my teacher wrote it.

would the answer be: 7^2+2(7) = 49+14 = 63?

Answer 3

no, since h(x) = 7, it means no matter what you put in for x, the answer will be 7
so h(D(x)) = 7