Andy and Simon had 64 marbles in total. Andy had 28 marbles less than Simon at first. After Andy and Simon played a game with Hilda, Andy had ¹₅ as many marbles as Simon. If Andy lost as many marbles as Simon to Hilda, find the number of marbles that Simon lost to Hilda.

	Andy	Simon	Difference
Before	1 u	1 u + 28	28
Change	- ?	- ?
After	1 p	5 p	4 p

Total number of marbles at first
= 1 u + 1 u + 28 
= 2 u + 28

2 u + 28 = 64
2 u = 64 - 28
2 u = 36

1 u = 36 ÷ 2 = 18

Since Andy lost the same number of marbles as Simon, the difference in the number of marbles between Andy and Simon at first and in the end remains the same.

Difference in the number of marbles in the end
= 5 p - 1 p
= 4 p

4 p = 28

1 p = 28 ÷ 4 = 7

Number of marbles that Andy lost to Hilda
= 1 u - 1 p
= 18 - 1 x 7
= 18 - 7
= 11

Since Simon lost the same number of marbles as Andy, the number of marbles that each lost to Hilda is the same.

Number of marbles that Simon lost = 11

Answer(s): 11