-3x+15=0
Add -15 both sides
-3x=-15
Divided by -3 both sides
x=-15/-3
x=5

$x^2(x+1)+2(x+1)=(x^2+2)(x+1)$
Does this say 8 × 3n/12=13? I want to be sure so I don't give you the wrong answer.
Are there any answers choices or is this question your own answer?