Distribute the multiplication:
$w\left(w-7\right)$w(w−7)
$-r\left(r+1\right)$−r(r+1)
$3a\left(a-16\right)$3a(a−16)
$-5t\left(5t-10\right)$−5t(5t−10)
Understand that polynomials form a system analogous to the integers, namely, they are closed under the operations of addition, subtraction, and multiplication; add, subtract, and multiply polynomials.