Olivia and Fabian collect pens and erasers. Fabian has 70 more erasers than pens. Fabian has 4 times the number of pens Olivia has, and Olivia has 30% more erasers than Fabian. After Olivia gives Fabian all of her pens and Fabian gives Olivia 60% of his erasers, Fabian has 40 more pens than erasers. Find the number of erasers Olivia has at first.

Olivia		Fabian
Erasers	Pens	Erasers	Pens
5.2 u + 91	1 u	4 u + 70	4 u
+ 2.4 u + 42	- 1 u	- 2.4 u - 42	+ 1 u
7.6 u + 133	0	1.6 u + 28	5 u

100% + 30% = 130% 

130% x 4 u
= ¹³⁰₁₀₀ x 4 u
= 5.2 u

130% x 70
= ¹³⁰₁₀₀ x 70
= 91 

60% x 4 u
= ⁶⁰₁₀₀ x 4 u
= 2.4 u  

60% x 70 
= ⁶⁰₁₀₀ x 70
= 42 

If another 40 erasers are given to Fabian, he will have equal number of erasers and pens in the end.
5 u = 1.6 u + 28 + 40
5 u - 1.6 u = 68
3.4 u = 68

1 u = 68 ÷ 3.4 = 20

Number of erasers that Olivia has at first
= 5.2 u + 91
= 5.2 x 20 + 91
= 104 + 91
= 195
 
Answer(s): 195