If $a(x+2)+b(x+2)=60$ and $a+b=12$, then $x$ is equal to
(A) 3
(B) 5
(C) 1
(D) 7
(E) 48
The equation $a(x+2)+b(x+2)=60$ has a common factor of $x+2$ on the left side.

Thus, we can re-write the equation as $(a+b)(x+2)=60$.

When $a+b=12$, we obtain $12 \cdot(x+2)=60$ and so $x+2=5$ which gives $x=3$.

ANSWER: (A)