If Eva gives Oliver $37, the amount of money she has will be 30% of his. If Oliver gives Eva $33, he will have the same amount of money as her. How much money did each of them have?
(a) Oliver
(b) Eva

	Case 1		Case 2
	Oliver	Eva	Oliver	Eva
Before	10 u - 37	3 u + 37	6.5 u + 33	6.5 u - 33
Change	+ 37	- 37	- 33	+ 33
After	10 u	3 u	6.5 u	6.5 u

(a)
30% = ³⁰₁₀₀ = ³₁₀

In Case 1, when Eva gives to Oliver, there is an internal transfer of money from Eva to Oliver.  The total amount that both have remains the same.

In Case 2, when Oliver gives to Eva, there is an internal transfer of money from Oliver to Eva. The total amount that both have remains the same.

The total amount that both have in Case 1 and Case 2 are the same.

Total amount that Eva and Oliver have
= 10 u + 3 u
= 13 u

Amount that Eva and Oliver each has in the end for Case 2
= 13 u ÷ 2
= 6.5 u

Amount that Oliver has at first is the same in Case 1 and Case 2.

10 u - 37 = 6.5 u + 33
10 u - 6.5 u = 33 + 37
3.5 u = 70 

1 u = 70 ÷ 3.5 = 20

Amount that Oliver has
= 10 u - 37
= 10 x 20 - 37
= 200 - 37
= $163 

(b)
Amount that Eva has
= 3 u + 37
= 3 x 20 + 37
= 60 + 37
= $97

Answer(s): (a) $163; (b) $97