Ken can do 20 sit-ups without stopping. Nathan can do twice as many, and Bob can do half the number of Ken and Nathan's combined sit-ups. How many more sit-ups can Bob do compared to Ken?
Nathan can do 20 x 2 = <T>multiply(20, 2)=40 sit ups.
Ken and Nathan's combined number is 20 + 40 = <T>add(20, 40)=60 sit-ups.
Bob can do 60/2 = <T>divide(60, 2)=30.0 sit-ups.
Bob can do 30 - 20 = <T>subtract(30, 20)=10 more sit-ups than Ken.
