Riordan, Sean and Bryan bought some cookies. After Riordan ate ³₇ of his cookies, Sean ate ³₄ of his cookies and Bryan ate 7 cookies, each of them had the same number of cookies left. Riordan had 18 less cookies than Sean at first.

1. How many cookies did Riordan have at first?
2. How many cookies did the 3 of them buy altogether? 

	Riordan	Sean	Bryan
Before	7 u	4x4 = 16 u	4 u + 7
Change	- 3 u	- 3x4 = - 12 u	- 7
After	4 u	1x4 = 4 u	4 u

(a)
The number of cookies that Riordan and Sean each had in the end is the same. Make the number of cookies that Riordan and Sean each had in the end the same.  LCM of 4 and 1 is 4.

Number of cookies that Riordan had less than Sean at first
= 16 u - 7 u
= 9 u

9 u = 18

1 u = 18 ÷ 9 = 2

Number of cookies that Riordan had at first
= 7 u
= 7 x 2
= 14 

(b)
Total number of cookies that the 3 of them bought
= 7 u + 16 u + 4 u + 7
= 27 u + 7
= 27 x 2 + 7
= 54 + 7
= 61

Answer(s): (a) 14; (b) 61