If $a=5$ and $a^{2}+a b=60$, the value of $b$ is
(A) 7
(B) 4
(C) 2
(D) 10
(E) 30
Substituting the given value of $a$, we obtain

$$
\begin{aligned}
a^{2}+a b & =60 \\
25+5 b & =60 \\
5 b & =35 \\
b & =7
\end{aligned}
$$

ANSWER: (A)