Answer
$(3x + 8)(3x + 4)$
Work Step by Step
For this problem, we can note $y= 3x +2$. So we have:
$$(3x + 2)^{2} + 8 (3x + 2) + 12 = y^2+8y+12.$$Now we look for $2$ numbers with sum $8$ and product $12$. Those numbers are $6$ and $2$. We have: $$y^2+8y+12=(y+6)(y+2).$$ Now we get back to $x$: $$\begin{aligned}(y+6)(y+2)&=(3x + 2 + 6)(3x + 2 + 2)\\
&= (3x + 8)(3x + 4).\end{aligned}$$
