#### Answer

$(2s+3)(3t-5)$

#### Work Step by Step

Regroup:
$=(6st+9t)+(-10s-15)$
Factor out $3t$ in the first and $-5$ in the second group to obtain:
$=3t(2s+3)+(-5)(2s+3)$
Factor out $2s+3$ to obtain:
$=(2s+3)[3t+(-5)]
\\=\color{blue}{(2s+3)(3t-5)}$