Answer
$-9r^{3} + 5r^{2} +r -9$
Work Step by Step
Recall, standard form means that we write the monomials with the highest degrees first. In order to subtract monomials, we combine like terms, but we distribute the negative to all of the terms past the subtraction sign. Like terms are terms that have the same variable raised to the same power. Note, by this definition, numbers like 10 and 15 are also like terms as they both have a degree of 0. Thus, we combine like terms to obtain the answer:
$-9r^{3} + 5r^{2} +r -9$
