Winnie and Ryan collect buttons and pens. Ryan has 60 less buttons than pens. Ryan has 3 times the number of buttons Winnie has, and Winnie has 30% more pens than Ryan. After Winnie gives Ryan all of her buttons and Ryan gives Winnie 60% of his pens, Ryan has 4 less pens than buttons. Find the number of pens Winnie has at first.

Winnie		Ryan
Pens	Buttons	Pens	Buttons
3.9 u + 78	1 u	3 u + 60	3 u
+ 1.8 u + 36	- 1 u	- 1.8 u - 36	+ 1 u
5.7 u + 114	0	1.2 u + 24	4 u

100%+ 30% = 130% 

130% x 3 u
= ¹³⁰₁₀₀ x 3 u
= 3.9 u

130% x 60
= ¹³⁰₁₀₀ x 60
= 78 

60% x 3 u
= ⁶⁰₁₀₀ x 3 u
= 1.8 u  

60% x 60 
= ⁶⁰₁₀₀ x 60
= 36 

If another 4 pens are given to Ryan, he will have equal number of pens and buttons in the end.
4 u = 1.2 u + 24 + 4
4 u - 1.2 u = 28
2.8 u = 28

1 u = 28 ÷ 2.8 = 10

Number of pens that Winnie has at first
= 3.9 u + 78
= 3.9 x 10 + 78
= 39 + 78
= 117
 
Answer(s): 117