Mary and George collect buttons and erasers. George has 50 more erasers than buttons. George has 3 times the number of buttons Mary has, and Mary has 20% more erasers than George. After Mary gives George all of her buttons and George gives Mary 60% of his erasers, George has 22 more buttons than erasers. Find the number of erasers Mary has at first.

Mary		George
Erasers	Buttons	Erasers	Buttons
3.6 u + 60	1 u	3 u + 50	3 u
+ 1.8 u + 30	- 1 u	- 1.8 u - 30	+ 1 u
5.4 u + 90	0	1.2 u + 20	4 u

100% + 20% = 120% 

120% x 3 u
= ¹²⁰₁₀₀ x 3 u
= 3.6 u

120% x 50
= ¹²⁰₁₀₀ x 50
= 60 

60% x 3 u
= ⁶⁰₁₀₀ x 3 u
= 1.8 u  

60% x 50 
= ⁶⁰₁₀₀ x 50
= 30 

If another 22 erasers are given to George, he will have equal number of erasers and buttons in the end.
4 u = 1.2 u + 20 + 22
4 u - 1.2 u = 42
2.8 u = 42

1 u = 42 ÷ 2.8 = 15

Number of erasers that Mary has at first
= 3.6 u + 60
= 3.6 x 15 + 60
= 54 + 60
= 114
 
Answer(s): 114