If Tammy gives Lee $18, the amount of money she has will be 25% of his. If Lee gives Tammy $36, he will have the same amount of money as her. How much money did each of them have?
(a) Lee
(b) Tammy

	Case 1		Case 2
	Lee	Tammy	Lee	Tammy
Before	4 u - 18	1 u + 18	2.5 u + 36	2.5 u - 36
Change	+ 18	- 18	- 36	+ 36
After	4 u	1 u	2.5 u	2.5 u

(a)
25% = ²⁵₁₀₀ = ¹₄

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

In Case 2, when Lee gives to Tammy, there is an internal transfer of money from Lee 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 Lee have
= 4 u + 1 u
= 5 u

Amount that Tammy and Lee each has in the end for Case 2
= 5 u ÷ 2
= 2.5 u

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

4 u - 18 = 2.5 u + 36
4 u - 2.5 u = 36 + 18
1.5 u = 54 

1 u = 54 ÷ 1.5 = 36

Amount that Lee has
= 4 u - 18
= 4 x 36 - 18
= 144 - 18
= $126 

(b)
Amount that Tammy has
= 1 u + 18
= 1 x 36 + 18
= 36 + 18
= $54

Answer(s): (a) $126; (b) $54