This question uses the concept of the division.
Vivi, the band drummer, burns 765 calories in 3 hours. And she burns these calories at the same rate. Which means she burns the same amount of calories per hour.
Thus, the set up equation for this question will be:
Energy burnt in 3 hours=756 calories
Therefore, Energy burnt in 1 hour = Calories.
Thus, the required answer is that Vivi burns 252 Calories of energy per hour while drumming.