conversations.from: human
conversations.value: Please show me the solution for: 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?
conversations.from: assistant
conversations.value: Nathan can do 20 x 2 = 40 sit ups.
  Ken and Nathan's combined number is 20 + 40 = 60 sit-ups.
  Bob can do 60/2 = 30 sit-ups.
  Bob can do 30 - 20 = 10 more sit-ups than Ken.