Gabriel and Peter had 63 tarts altogether. After Gabriel ate ¹₃ of his tarts and Peter ate 7 tarts, the number of tarts Peter had left was twice the number of tarts Gabriel had left. How many more tarts did Peter have than Gabriel at first?

	Gabriel	Peter	Total
Before	3 u	4 u + 7	63
Change	- 1 u	- 7
After	2 u
Comparing Gabriel and Peter in the end	1x2 = 2 u	2x2 = 4 u

The number of tarts that Gabriel had in the end is the same. Make the number of tarts that Gabriel had in the end the same.  LCM of 2 and 1 is 2.

Total number of tarts at first
= 3 u + 4 u + 7
= 7 u + 7

7 u + 7 = 63
7 u = 63 - 7
7 u = 56 

1 u = 56 ÷ 7 = 8

Number of tarts that Gabriel had at first
= 3 u
= 3 x 8
= 24

Number of tarts that Peter had at first
= 63 - 24
= 39

Number of tarts that Peter had more than Gabriel at first
= 39 - 24
= 15

Answer(s): 15