Question

A 150-lb person burns about 2700 Calories to run a marathon. How much energy is burned in kJ?

Answer 1

Did you intend, I assume so, to write calorie with a capital C? That stands for 2700 kcal.
1 calorie = 4.184 joules.
1 kJ = 1000 J.

2700 kcal x 1000 = 2,700,000 cal.
2,700,000 cal x * (4.184 J/cal) x (1 kJ/1000 J)

Answer 2

11.30x10e7