Justin had an equal number of chocolate muffins, butter muffins and matcha muffins. After he ate 31 chocolate muffins, some butter muffins and matcha muffins, there were 55 muffins left. The number of butter muffins he ate was thrice the number of matcha muffins he ate. The number of butter muffins left was 16 more than the number of chocolate muffins left. How many chocolate muffins were there at first?

	Chocolate muffins	Butter muffins	Matcha muffins	Total muffins
Before	1 p + 31	1 p + 3 u + 16	1 p + 3 u + 16
Change	- 31	- 3 u	- 1 u
After	1 p	1 p + 16	1 p + 16 + 1 u	55

Number of butter muffins and chocolate muffins was equal at first.

1 p + 3 u + 16 = 1 p + 31
3 u = 31 - 16
3 u = 15

1 u = 15 ÷ 3 = 5

Total number of muffins in the end
= 1 p + 1 p + 16 + 1 p + 16 + 5
= 1 p + 1 p + 1 p + 16 + 16 + 5
= 3 p + 37

3 p + 37 = 55
3 p = 55 - 37
3 p = 18

1 p = 18 ÷ 3 = 6

Number of chocolate muffins at first
= 1 p + 31
= 6 + 31
= 37

Answer(s): 37