Answer
$y^{4}$
Work Step by Step
We are given the expression $\frac{y^{-3}}{y^{-7}}$. We can use the quotient rule to simplify, which holds that $\frac{a^{m}}{a^{n}}=a^{m-n}$ (where a is a nonzero real number, and m and n are integers).
$\frac{y^{-3}}{y^{-7}}=y^{-3-(-7)}=y^{4}$