Mark and David had 35 scones altogether. After Mark ate ¹₅ of his scones and David ate 9 scones, the number of scones David had left was twice the number of scones Mark had left. How many more scones did David have than Mark at first?

	Mark	David	Total
Before	5 u	8 u + 9	35
Change	- 1 u	- 9
After	4 u
Comparing Mark and David in the end	1x4 = 4 u	2x4 = 8 u

The number of scones that Mark had in the end is the same. Make the number of scones that Mark had in the end the same.  LCM of 4 and 1 is 4.

Total number of scones at first
= 5 u + 8 u + 9
= 13 u + 9

13 u + 9 = 35
13 u = 35 - 9
13 u = 26 

1 u = 26 ÷ 13 = 2

Number of scones that Mark had at first
= 5 u
= 5 x 2
= 10

Number of scones that David had at first
= 35 - 10
= 25

Number of scones that David had more than Mark at first
= 25 - 10
= 15

Answer(s): 15