Debby made 67 hamburgers, sandwiches and pineapple pies. 20 of them were hamburgers and 24 of them were sandwiches. How many pineapple pies there?

pineapple pies

The number of hamburgers and sandwiches: 20 + 24 = 44

So, the number of pineapple pies: 67 - 44 = 23