Properties of Definite Integrals

If $\displaystyle\int_{0}^{6} r(x)\,dx = 15$ and $\displaystyle\int_{0}^{6} s(x)\,dx = -9$, what is the value of $\displaystyle\int_{6}^{0} \left(4r(x) + 3s(x)\right)\,dx$?