# How do you factor by grouping: 8st+12t-10s-15?

You can try collecting $2 s$ from the first and third term and $3$ from the second and fourth:
$2 s \left(4 t - 5\right) + 3 \left(4 t - 5\right) =$
$\left(4 t - 5\right) \left(2 s + 3\right)$