Let's use X to represent amount of distance we do not know, the amount of distance to the beach.

he drives 5 miles to the beach, plus X miles to the beach for a total of 12 miles.

X + 5= 12

Now, lets figure out what X is. To figure out what X is, you have to get it by itself.

To do this, subtract 5 from both sides.

X + 5 -5= 12 -5

X = 7.

7 miles to the beach.