Yoko and Risa have some cupcakes each. If Yoko gives Risa 17 cupcakes, Yoko will have ⁶₇ as many cupcakes as Risa. If Yoko gives Risa 12 cupcakes, they will have an equal number of cupcakes. How many cupcakes does Yoko have at first?

	Case 1		Case 2
	Yoko	Risa	Yoko	Risa
Before	6 u + 17	7 u - 17	6.5 u + 12	6.5 u - 12
Change	- 17	+ 17	- 12	+ 12
After	6 u	7 u	6.5 u	6.5 u

Total number of cupcakes that Yoko and Risa have
= 6 u + 7 u
= 13 u 

Number of cupcakes that Yoko and Risa each has in the end is the same.

Number of cupcakes that Yoko and Risa each has in the end in Case 2
= 13 u ÷ 2
= 6.5 u

Number of cupcakes that Yoko had at first is the same in Case 1 and Case 2.

6.5 u + 12 = 6 u + 17
6.5 u - 6 u = 17 - 12
0.5 u = 5

1 u = 5 ÷ 0.5 = 10

Number of cupcakes that Yoko has
= 6 u + 17
= 6 x 10 + 17
= 60 + 17
= 77

Answer(s): 77