This is factor by grouping. In factor by grouping, write a quadratic trinomil as 4 terms and group by parenthesis. Then factor by GCF in each pair. If the two parenthesis match, the factoring has worked and the factors will be the GCFs as one and the parenthesis as one other.
The factors here are the GCFs and -3 as and the parenthesis (x-5).