Answer
$8y(y-3)$.
Work Step by Step
The given expression is
$=8y^2-24y$
The GCF of $8$ and $24$ is $8$.
The GCF of $y^2$ and $y$ is $y$.
So, the greatest common monomial factor of the terms is $8y$.
Hence, the factor form is $8y(y-3)$.