Anna and Vaidev collect pencils and pens. Vaidev has 52 more pens than pencils. Vaidev has 3 times the number of pencils Anna has, and Anna has 25% more pens than Vaidev. After Anna gives Vaidev all of her pencils and Vaidev gives Anna 75% of his pens, Vaidev has 39 more pencils than pens. Find the number of pens Anna has at first.

Anna		Vaidev
Pens	Pencils	Pens	Pencils
3.75 u + 65	1 u	3 u + 52	3 u
+ 2.25 u + 39	- 1 u	- 2.25 u - 39	+ 1 u
6 u + 104	0	0.75 u + 13	4 u

100% + 25% = 125% 

125% x 3 u
= ¹²⁵₁₀₀ x 3 u
= 3.75 u

125% x 52
= ¹²⁵₁₀₀ x 52
= 65 

75% x 3 u
= ⁷⁵₁₀₀ x 3 u
= 2.25 u  

75% x 52 
= ⁷⁵₁₀₀ x 52
= 39 

If another 39 pens are given to Vaidev, he will have equal number of pens and pencils in the end.
4 u = 0.75 u + 13 + 39
4 u - 0.75 u = 52
3.25 u = 52

1 u = 52 ÷ 3.25 = 16

Number of pens that Anna has at first
= 3.75 u + 65
= 3.75 x 16 + 65
= 60 + 65
= 125
 
Answer(s): 125