If Tammy gives Simon $39, the amount of money she has will be 30% of his. If Simon gives Tammy $66, he will have the same amount of money as her. How much money did each of them have?
(a) Simon
(b) Tammy

	Case 1		Case 2
	Simon	Tammy	Simon	Tammy
Before	10 u - 39	3 u + 39	6.5 u + 66	6.5 u - 66
Change	+ 39	- 39	- 66	+ 66
After	10 u	3 u	6.5 u	6.5 u

(a)
30% = ³⁰₁₀₀ = ³₁₀

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

In Case 2, when Simon gives to Tammy, there is an internal transfer of money from Simon to Tammy. 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 Tammy and Simon have
= 10 u + 3 u
= 13 u

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

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

10 u - 39 = 6.5 u + 66
10 u - 6.5 u = 66 + 39
3.5 u = 105 

1 u = 105 ÷ 3.5 = 30

Amount that Simon has
= 10 u - 39
= 10 x 30 - 39
= 300 - 39
= $261 

(b)
Amount that Tammy has
= 3 u + 39
= 3 x 30 + 39
= 90 + 39
= $129

Answer(s): (a) $261; (b) $129