Cindy and Pierre collect stickers and coins. Pierre has 40 more coins than stickers. Pierre has 4 times the number of stickers Cindy has, and Cindy has 40% more coins than Pierre. After Cindy gives Pierre all of her stickers and Pierre gives Cindy 70% of his coins, Pierre has 7 more stickers than coins. Find the number of coins Cindy has at first.

Cindy		Pierre
Coins	Stickers	Coins	Stickers
5.6 u + 56	1 u	4 u + 40	4 u
+ 2.8 u + 28	- 1 u	- 2.8 u - 28	+ 1 u
8.4 u + 84	0	1.2 u + 12	5 u

100% + 40% = 140% 

140% x 4 u
= ¹⁴⁰₁₀₀ x 4 u
= 5.6 u

140% x 40
= ¹⁴⁰₁₀₀ x 40
= 56 

70% x 4 u
= ⁷⁰₁₀₀ x 4 u
= 2.8 u  

70% x 40 
= ⁷⁰₁₀₀ x 40
= 28 

If another 7 coins are given to Pierre, he will have equal number of coins and stickers in the end.
5 u = 1.2 u + 12 + 7
5 u - 1.2 u = 19
3.8 u = 19

1 u = 19 ÷ 3.8 = 5

Number of coins that Cindy has at first
= 5.6 u + 56
= 5.6 x 5 + 56
= 28 + 56
= 84
 
Answer(s): 84