Usha and Sam collect cards and erasers. Sam has 30 less cards than erasers. Sam has 4 times the number of cards Usha has, and Usha has 40% more erasers than Sam. After Usha gives Sam all of her cards and Sam gives Usha 60% of his erasers, Sam has 39 less erasers than cards. Find the number of erasers Usha has at first.

Usha		Sam
Erasers	Cards	Erasers	Cards
5.6 u + 42	1 u	4 u + 30	4 u
+ 2.4 u + 18	- 1 u	- 2.4 u - 18	+ 1 u
8 u + 60	0	1.6 u + 12	5 u

100%+ 40% = 140% 

140% x 4 u
= ¹⁴⁰₁₀₀ x 4 u
= 5.6 u

140% x 30
= ¹⁴⁰₁₀₀ x 30
= 42 

60% x 4 u
= ⁶⁰₁₀₀ x 4 u
= 2.4 u  

60% x 30 
= ⁶⁰₁₀₀ x 30
= 18 

If another 39 erasers are given to Sam, he will have equal number of erasers and cards in the end.
5 u = 1.6 u + 12 + 39
5 u - 1.6 u = 51
3.4 u = 51

1 u = 51 ÷ 3.4 = 15

Number of erasers that Usha has at first
= 5.6 u + 42
= 5.6 x 15 + 42
= 84 + 42
= 126
 
Answer(s): 126