Aroad sign gives drivers information about traffic on busy highways. one sign shows "15 miles in 20 minutes". what is this speed in miles pee hours?

First of all you need to work out 20 minutes in hours, this can be done by dividing 20 by 60:
20/60 = 1/3

Then you need to divide 15 by 1/3 to get the final speed:
15 / 1/3 = 45 miles per hour

He will need to be traveling at 45 miles per hour,
Hope this helps! :)