The whole pie is 1, because 1 is 100%. Tom ate 2/3 of 1 and Sam ate 1/4 of the pie. So, here's how to determine how much is left: 1 - (2/3 + 1/4) = 1 - (8/12 + 3/12) = 1 - 11/12 = 12/12 - 11/12 = 1/12
The correct answer is that 1/2 of the pie is left.
