Ben had an equal number of matcha cookies, blueberry cookies and cream cookies. After he ate 20 matcha cookies, some blueberry cookies and cream cookies, there were 31 cookies left. The number of blueberry cookies he ate was thrice the number of cream cookies he ate. The number of blueberry cookies left was 11 more than the number of matcha cookies left. How many matcha cookies were there at first?

	Matcha cookies	Blueberry cookies	Cream cookies	Total cookies
Before	1 p + 20	1 p + 3 u + 11	1 p + 3 u + 11
Change	- 20	- 3 u	- 1 u
After	1 p	1 p + 11	1 p + 11 + 1 u	31

Number of blueberry cookies and matcha cookies was equal at first.

1 p + 3 u + 11 = 1 p + 20
3 u = 20 - 11
3 u = 9

1 u = 9 ÷ 3 = 3

Total number of cookies in the end
= 1 p + 1 p + 11 + 1 p + 11 + 3
= 1 p + 1 p + 1 p + 11 + 11 + 3
= 3 p + 25

3 p + 25 = 31
3 p = 31 - 25
3 p = 6

1 p = 6 ÷ 3 = 2

Number of matcha cookies at first
= 1 p + 20
= 2 + 20
= 22

Answer(s): 22