To four places of decimals $\sqrt{56} = 7.4833\;\mbox{ and }\; \sqrt{58} = 7.6158$
If $\sqrt{56} < \frac{p}{q} < \sqrt{58}$, then $56q^2 < p^2< 58q^2$
Try different values of $q$, and remember $p$ is a whole number.