First you must convert the rates to the same units. I choose to convert Ben's rate to mph.
(1/10) miles per minute = 6 mph
Both boys will ravel for the same amount of time, T and they will travel 2 miles in total
6T + (1/40)T = 2 => 241T = 80
and T = 80/241 hrs...a little less than 20 minutes!