Reggie has 90% as many marbles as Brandon. If Reggie gives away 50% of the marbles and Brandon gives away 70% of his marbles, they will have 30 marbles altogether. How many marbles do the two of them have?

	Reggie	Brandon	Total
Comparing Reggie and Brandon at first	9x2 = 18 u	10x2 = 20 u
Before	2x9 = 18 u	10x2 =  20 u
Change	- 1x9 = - 9 u	- 7x2 = - 14 u
After	1x9 = 9 u	3x2 = 6 u	30

90% = ⁹⁰₁₀₀ = ⁹₁₀

50% = ⁵⁰₁₀₀ = ¹₂ 

70% =⁷⁰₁₀₀ = ⁷₁₀ 

The number of marbles that Reggie has at first is repeated.  Make the number of marbles that Reggie has the same.  LCM of 9 and 2 is 18 u.

The number of marbles that Brandon has at first is repeated. Make the number of marbles that Brandon has the same. LCM of 10 and 10 is 20 u.

Number of marbles in the end
= 9 u + 6 u
= 15 u

15 u = 30

1 u = 30 ÷ 15 = 2

Total number of marbles that the two of them have
= 18 u + 20 u
= 38 u
= 38 x 2
= 76

Answer(s): 76