Here, you’re going to be focusing on the function d. The expression there wants you to evaluate d at the value 2a, and then multiply the result by 5. Substituting the x’s in d(x) with 2a:
-(2a)^3+2a+1 = -8a^3+2a+1
Multiplying that polynomial by 5, we get:
-40a^3+10a+5