Fred had an equal number of strawberry tarts, chocolate tarts and vanila tarts. After he ate 35 strawberry tarts, some chocolate tarts and vanila tarts, there were 56 tarts left. The number of chocolate tarts he ate was four times the number of vanila tarts he ate. The number of chocolate tarts left was 15 more than the number of strawberry tarts left. How many strawberry tarts were there at first?

	Strawberry tarts	Chocolate tarts	Vanila tarts	Total tarts
Before	1 p + 35	1 p + 4 u + 15	1 p + 4 u + 15
Change	- 35	- 4 u	- 1 u
After	1 p	1 p + 15	1 p + 15 + 1 u	56

Number of chocolate tarts and strawberry tarts was equal at first.

1 p + 4 u + 15 = 1 p + 35
4 u = 35 - 15
4 u = 20

1 u = 20 ÷ 4 = 5

Total number of tarts in the end
= 1 p + 1 p + 15 + 1 p + 15 + 5
= 1 p + 1 p + 1 p + 15 + 15 + 5
= 3 p + 35

3 p + 35 = 56
3 p = 56 - 35
3 p = 21

1 p = 21 ÷ 3 = 7

Number of strawberry tarts at first
= 1 p + 35
= 7 + 35
= 42

Answer(s): 42