Joe drives 20 mi-in 1/2 h. how long will it take him to derive 50 mi?

An hour and 15 minutes.  Since Joe is driving 20 miles per 1/2 hour that means he is driving 40 miles every hour. We still have 10 miles left and since 20 divided by 2 is ten you would simply cut the time it takes him to drive 20 miles in half making 15 minutes. Then you add the time it takes to drive 40 miles and 10 miles and that's how you get an hour and 15 minutes. Hope this made sense!