You can
put this solution on YOUR website!d = distance from cs to pp
6 mi/hr = average rate cs to pp
15 mi/hr = average rate pp to cs
t + 1.5 = time in hours cs to pp
t = time in hours pp to cs
[1]

[2]

set [1] equal to [2]

t + 1.5 = time in hours cs to pp
1 + 1.5 = 2.5 hrs
check

OK