Energyintake,
The key is the Speed = Distance/Time equation.
In this case it is slightly complicated because you need to be able to express 2 hours 36 minutes as a fraction in terms of hours only (i.e. no minutes). To do this you need to identify 36 as a fraction of 60 minutes. If you get used to numbers which are whole factors of 60 minutes you will find this gets easier: the key numbers are 2, 3, 4, 5, 6, 10 & 12. In 60 minutes there are 2 x 30 minute periods, 3 x 20 minute periods, 4 x 15 minute periods, 5 x 12 minute periods, 6 x 10 minute periods, 10 x 6 minute periods, 12 x 5 minute periods... etc. (you could keep going but the numbers become less helpful for standard examples).
In this example we can see that 36 is a multiple of 6 (6x6=36) which corresponds with the factor of 10, so we can describe 36 minutes as 6/10 of a hour.
Having worked this out you can now define your time period purely in terms of a number of hours (no minutes) - 2 hours 36 minutes becomes 2+(6/10) hours or 26/10 hours.
Now you just put this into the equation: Speed = 65/(26/10)
= 650/26
= 25 mph