Xandra has 30% as many marbles as Gwen. Gwen has 140% as many marbles as Yen. If Gwen gives 30 marbles to Yen, both will then have an equal number of marbles. Find the average number of marbles the three of them have.

Xandra	Gwen	Yen
3x7	10x7
	7x10	5x10
21 u	70 u	50 u

30% = ³⁰₁₀₀ = ³₁₀
140% = ¹⁴⁰₁₀₀= ⁷₅

The number of marbles that Xandra has is repeated.  Make the number of marbles that Xandra has the same. LCM of 10 and 7 is 70.

	Gwen	Yen	Total
Before	70 u	50 u	120 u
Change	- 10 u	+ 10 u
After	60 u	60 u	120 u

Total number of marbles that Gwen and Yen have
= 70 u + 50 u
= 120 u

After Gwen gives to Yen, both of them will have the same number of marbles. 

The total number of marbles that Gwen and Yen have remains unchanged.

Number of marbles that each of them will have
= 120 u ÷ 2
= 60 u

Number of marbles that Gwen gives to Yen
= 70 u - 60 u
= 10 u

10 u = 30

1 u = 30 ÷ 10 = 3

Total number of marbles that three of them have
= 120 u + 21 u
= 141 u

Average number of marbles that each of them have
= 141 u ÷ 3
= 47 u
= 47 x 3
= 141

Answer(s): 141