Elijah and Seth had 101 marbles in total. Elijah had 35 marbles less than Seth at first. After Elijah and Seth played a game with Irene, Elijah had ⁴₁₁ as many marbles as Seth. If Elijah lost as many marbles as Seth to Irene, find the number of marbles that Seth lost to Irene.

	Elijah	Seth	Difference
Before	1 u	1 u + 35	35
Change	- ?	- ?
After	4 p	11 p	7 p

Total number of marbles at first
= 1 u + 1 u + 35 
= 2 u + 35

2 u + 35 = 101
2 u = 101 - 35
2 u = 66

1 u = 66 ÷ 2 = 33

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

Difference in the number of marbles in the end
= 11 p - 4 p
= 7 p

7 p = 35

1 p = 35 ÷ 7 = 5

Number of marbles that Elijah lost to Irene
= 1 u - 4 p
= 33 - 4 x 5
= 33 - 20
= 13

Since Seth lost the same number of marbles as Elijah, the number of marbles that each lost to Irene is the same.

Number of marbles that Seth lost = 13

Answer(s): 13