Joelle and Lee collect marbles and pens. Lee has 80 less marbles than pens. Lee has 3 times the number of marbles Joelle has, and Joelle has 20% more pens than Lee. After Joelle gives Lee all of her marbles and Lee gives Joelle 70% of his pens, Lee has 38 more marbles than pens. Find the number of pens Joelle has at first.

Joelle		Lee
Pens	Marbles	Pens	Marbles
3.6 u + 96	1 u	3 u + 80	3 u
+ 2.1 u + 56	- 1 u	- 2.1 u - 56	+ 1 u
5.7 u + 152	0	0.9 u + 24	4 u

100%+ 20% = 120% 

120% x 3 u
= ¹²⁰₁₀₀ x 3 u
= 3.6 u

120% x 80
= ¹²⁰₁₀₀ x 80
= 96 

70% x 3 u
= ⁷⁰₁₀₀ x 3 u
= 2.1 u  

70% x 80 
= ⁷⁰₁₀₀ x 80
= 56 

If another 38 pens are given to Lee, he will have equal number of pens and marbles in the end.
4 u = 0.9 u + 24 + 38
4 u - 0.9 u = 62
3.1 u = 62

1 u = 62 ÷ 3.1 = 20

Number of pens that Joelle has at first
= 3.6 u + 96
= 3.6 x 20 + 96
= 72 + 96
= 168
 
Answer(s): 168