Correction:
Decide the coefficient before x and x^3 when (x^2+7x+7)(x^3−5x+3x) develops.
Firstly, what do you mean by the term "develops"? If its multiplication then
multiply the factors yourself to get the answers. This is pretty much basic algebra. The only thing you have to watch here is that when the terms x^{3} and x comes while doing the multiplication.
I can show you the way only.
(x^2+7x+7)(x^3-5x+3x)
=(x^2+7x+7)(x^3-2x)
=x^2(x^3-2x)+7x(x^3-2x)+7(x^3-2x)
Now can you do it ?