The average weight of 5 men decreases by 3 kg when one of them weighing 150 kg is replaced by another person. Find the weight of the new person.

135 kg

Lets assume, average  weight of 5 men is x kg

                   and Weight of new person is y kg

So, 5x-150 +y = 5 (x-3)

                   y = 135

Hence weight of new person is 135 Kg