Sabrina and Xylia have some wafers each. If Sabrina gives Xylia 7 wafers, Sabrina will have ²₃ as many wafers as Xylia. If Sabrina gives Xylia 4 wafers, they will have an equal number of wafers. How many wafers does Sabrina have at first?

	Case 1		Case 2
	Sabrina	Xylia	Sabrina	Xylia
Before	2 u + 7	3 u - 7	2.5 u + 4	2.5 u - 4
Change	- 7	+ 7	- 4	+ 4
After	2 u	3 u	2.5 u	2.5 u

Total number of wafers that Sabrina and Xylia have
= 2 u + 3 u
= 5 u 

Number of wafers that Sabrina and Xylia each has in the end is the same.

Number of wafers that Sabrina and Xylia each has in the end in Case 2
= 5 u ÷ 2
= 2.5 u

Number of wafers that Sabrina had at first is the same in Case 1 and Case 2.

2.5 u + 4 = 2 u + 7
2.5 u - 2 u = 7 - 4
0.5 u = 3

1 u = 3 ÷ 0.5 = 6

Number of wafers that Sabrina has
= 2 u + 7
= 2 x 6 + 7
= 12 + 7
= 19

Answer(s): 19