Algebra

Let t be the time it takes to drive to the beach. We have

$40\ mph\cdot t=55\ mph(t-25\ min)\\ 40t=55t-1375\ min\\ 15t=1375\ min\\ t=91\frac{2}{3}\ min$

Now, we know that $s=v\cdot t$ from our speed formulas. We just have to plug the values in!

We have 

$s=v\cdot t=40\ mph\cdot 91\frac{2}{3}\ min\cdot \frac{h}{60\ min}\\ s=61 \frac{1}{9}\ miles$

Thanks! :)