It would be 90 minutes, but you can figure this out by doing a fraction:
40 miles/ 60 minutes = 60 miles / x
If you cross multiply, you do 60 times 60 and 40 times x.
3,600 = 40x
You now need to divide by 40 on each side so that you can find the value for x.
3,600/40 = 90 = x