Ivory and Oliver collect stickers and pens. Oliver has 45 more pens than stickers. Oliver has 4 times the number of stickers Ivory has, and Ivory has 20% more pens than Oliver. After Ivory gives Oliver all of her stickers and Oliver gives Ivory 60% of his pens, Oliver has 16 more stickers than pens. Find the number of pens Ivory has at first.

Ivory		Oliver
Pens	Stickers	Pens	Stickers
4.8 u + 54	1 u	4 u + 45	4 u
+ 2.4 u + 27	- 1 u	- 2.4 u - 27	+ 1 u
7.2 u + 81	0	1.6 u + 18	5 u

100% + 20% = 120% 

120% x 4 u
= ¹²⁰₁₀₀ x 4 u
= 4.8 u

120% x 45
= ¹²⁰₁₀₀ x 45
= 54 

60% x 4 u
= ⁶⁰₁₀₀ x 4 u
= 2.4 u  

60% x 45 
= ⁶⁰₁₀₀ x 45
= 27 

If another 16 pens are given to Oliver, he will have equal number of pens and stickers in the end.
5 u = 1.6 u + 18 + 16
5 u - 1.6 u = 34
3.4 u = 34

1 u = 34 ÷ 3.4 = 10

Number of pens that Ivory has at first
= 4.8 u + 54
= 4.8 x 10 + 54
= 48 + 54
= 102
 
Answer(s): 102