John ordered a pizza and ate 23 of the pizza. Also, he gave 16 of the whole pizza to his sister. Then what part of the pizza is left with John?
16
Amount of pizza eaten by John =23
Amount of pizza given to his sister =16
∴ The total amount of pizza eaten by John and his sister =23+16=4+16=56
∴ The amount of pizza left with john =1−56=6−56=16