Sarah and Bobby collect coins and marbles. Bobby has 88 more marbles than coins. Bobby has 2 times the number of coins Sarah has, and Sarah has 25% more marbles than Bobby. After Sarah gives Bobby all of her coins and Bobby gives Sarah 75% of his marbles, Bobby has 8 more coins than marbles. Find the number of marbles Sarah has at first.

Sarah		Bobby
Marbles	Coins	Marbles	Coins
2.5 u + 110	1 u	2 u + 88	2 u
+ 1.5 u + 66	- 1 u	- 1.5 u - 66	+ 1 u
4 u + 176	0	0.5 u + 22	3 u

100% + 25% = 125% 

125% x 2 u
= ¹²⁵₁₀₀ x 2 u
= 2.5 u

125% x 88
= ¹²⁵₁₀₀ x 88
= 110 

75% x 2 u
= ⁷⁵₁₀₀ x 2 u
= 1.5 u  

75% x 88 
= ⁷⁵₁₀₀ x 88
= 66 

If another 8 marbles are given to Bobby, he will have equal number of marbles and coins in the end.
3 u = 0.5 u + 22 + 8
3 u - 0.5 u = 30
2.5 u = 30

1 u = 30 ÷ 2.5 = 12

Number of marbles that Sarah has at first
= 2.5 u + 110
= 2.5 x 12 + 110
= 30 + 110
= 140
 
Answer(s): 140