Question 162868
x(x+2)-3=12
x^2+2x-3=12
x^2+2x-3-12=0
x^2+2x-15=0
(x+5)(x-3)=0
x+5=0 
x=-5 answer.
x-3=0
x=3 answer.
Proofs:
-5(-5+2)-3=12
-5*-3-3=12
15-3=12
12=12
3(3+2)-3=12
3*5-3=12
15-3=12
12=12