jmc

Let $a$ be Andrew's age now and $g$ be his grandfather's age now. We are looking for the value of $a$. We can set up a system of two equations to represent the given information, as follows:

$$\begin{array}{rl}g& =8a\\ g-a& =56\end{array}$$In particular, the second equation represents the grandfather's age $a$ years ago, when Andrew was born. To solve for $a$, we need to eliminate $g$ from the equations above. Substituting the first equation into the second to eliminate $g$, we get that $8a-a=56$ or $a=8$. Thus, Andrew is $\boxed{8}$ years old now.