Seth had an equal number of vanila cookies, cream cookies and chocolate cookies. After he ate 40 vanila cookies, some cream cookies and chocolate cookies, there were 36 cookies left. The number of cream cookies he ate was thrice the number of chocolate cookies he ate. The number of cream cookies left was 10 more than the number of vanila cookies left. How many vanila cookies were there at first?

	Vanila cookies	Cream cookies	Chocolate cookies	Total cookies
Before	1 p + 40	1 p + 3 u + 10	1 p + 3 u + 10
Change	- 40	- 3 u	- 1 u
After	1 p	1 p + 10	1 p + 10 + 1 u	36

Number of cream cookies and vanila cookies was equal at first.

1 p + 3 u + 10 = 1 p + 40
3 u = 40 - 10
3 u = 30

1 u = 30 ÷ 3 = 10

Total number of cookies in the end
= 1 p + 1 p + 10 + 1 p + 10 + 10
= 1 p + 1 p + 1 p + 10 + 10 + 10
= 3 p + 30

3 p + 30 = 36
3 p = 36 - 30
3 p = 6

1 p = 6 ÷ 3 = 2

Number of vanila cookies at first
= 1 p + 40
= 2 + 40
= 42

Answer(s): 42