Question 969841
This is a proportion problem.

(3/28) =( x/42)

Cross-multiply:  42*3=28*x

126=28*x

x=(126/28) =4.5 miles

This works, because 42 minutes is half again of 28 (28+14).
Four and a half miles is half again of 3 (3+1.5).  This is another way to do it.