Final answer:
The subject of this question is Mathematics. The equation provided represents the average calories burned for a person when exercising.
Step-by-step explanation:
The subject of this question is Mathematics. The equation provided in the question, calories = x² - 12x + 36, represents the average calories burned for a person when exercising. The equation is a quadratic equation, where x represents the amount of exercise. By plugging in different values of x, you can find the corresponding average calories burned.