For this, you have to memorize the formula a^2+b^2=c^2.
The bottom side of the box has 8 boxes, so 8 square miles (12 minutes)
The left side has 14 boxes, 14 square miles. (28 minutes)
Using the formula, it goes like this: (8)^2+(14)^2=c^2
Find c:
64+196=c^2
c= 16.124
So the hypotenuse is 16.124 square miles (an exact number), so if you have a calculator, we can now find how many minutes he can drive using the shortcut:
16.124*2= 32.249 = 32.24 minutes.