Answer
$$-\frac{3}{8}rs^2+2rst.$$
Work Step by Step
By multiplying each term of the polynomial by the factor $-\frac{1}{8}rs$, and then adding the products, we have
$$
-\frac{1}{8}rs(3s-16t)=-\frac{1}{8}rs(3s)-\frac{1}{8}rs(-16t)\\
=-\frac{3}{8}rs^2+2rst.
$$
