Consider $wa+2bw+3a+6b$. Do the grouping $wa+2bw+3a+6b=\left(wa+2bw\right)+\left(3a+6b\right)$, and factor out $w$ in the first and $3$ in the second group.
$$w\left(a+2b\right)+3\left(a+2b\right)$$
Factor out common term $a+2b$ by using distributive property.
