How do you fill in the blank for the expression r^?*r^12=r^20?

Sep 30, 2015

r^?=r^8
Apply the exponent rule ${x}^{a} / {x}^{b} = {x}^{a - b}$ .
r^?=r^20/r^12=
r^?=r^((20-12))=r^8