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% ...