Zoe and Sabrina had a total of 70 erasers. Sabrina gave ¹₃ of her erasers to Zoe. In return, Zoe gave ¹₈ of the total number of erasers that she had to Sabrina. In the end, each girl had the same number of erasers. How many erasers did Zoe have at first?

	Zoe	Sabrina	Total
Before 1	?	3 u	70
Change 1	+ 1 u	- 1 u
After 1	40	2 u	70
Before 2	8 p	2 u	70
Change 2	- 1 p	+ 1 p
After 2	7 p (35)	35	70

Since Sabrina gave some erasers to Zoe and Zoe then gave some erasers to Sabrina, it is an internal transfer of erasers between the two girls. So, the total number of erasers remains unchanged.

Number of erasers that Sabrina and Zoe each had in the end is the same.

Number of erasers that Zoe had in the end
= 70 ÷ 2
= 35

Number of erasers that Zoe had in the end = 7 p

7 p = 35

1 p = 35 ÷ 7 = 5

Number of erasers that Zoe had after receiving some erasers from Sabrina
= 8 p
= 8 x 5
= 40

Number of erasers that Sabrina had after giving to Zoe
= 70 - 40
= 30

2 u = 30

1 u = 30 ÷ 2 = 15

Number of erasers that Sabrina had at first
= 3 u
= 3 x 15
= 45

Number of erasers that Zoe had at first
= 70 - 45
= 25

Answer(s): 25