136kg divided by 165 mins
flight time (2 hrs 45 mins) = 0,824 kg/min
30% of 136kg = 40,8kg reserve fuel.
40,8 / 0,824 = 49 mins.
2hrs 45 mins + 49 mins = 3 hrs 34 mins
Taxi fuel must be ignored because it has no influence
on endurance. It's been burned when taking off.
There seem to be several of these types of
question around .... reserve fuel is 30% of trip fuel
.... you are given trip time .... so
as this is all the information they give you, simply increase trip time by 30%
...