I understand integrals for the most part...but not sure what to do here.

Find the particular antiderivative that satisfies the following conditions:

$\displaystyle p'(x)=80/x^3$; $\displaystyle p(7)=8$

I know that $\displaystyle p(x)=-40/x^2$, but not sure where to go from there.

Thanks for your help guys,