Answer
$y^{15a+3}$
Work Step by Step
Using laws of exponents, the given expression simplifies to
\begin{align*}
&
\dfrac{\left( y^{2a} \right)^8}{y^{a-3}}
\\\\&=
\dfrac{y^{2a(8)}}{y^{a-3}}
\\\\&=
\dfrac{y^{16a}}{y^{a-3}}
\\\\&=
y^{16a-(a-3)}
\\\\&=
y^{16a-a+3}
\\\\&=
y^{15a+3}
.\end{align*}
