Let the speed at which John is going towards Leakey = x mph
Time taken to reach Leakey = 4 hours
Distance = speed * time
So let the distance of Leakey from John's house be 4x ............. (1)
Speed while returning was 20 mph less = (x-20)
Time taken was= 7 hours
distance = (x-20)*7 ................(2)
As the distance remains the same, equation 1 = equation 2
So, the speed is mph
Distance = 4x
=
Hence, the distance of Leakey from John's house is 186.667 miles.