Sabrina and Jean had a total of 70 pens. Jean gave ¹₄ of her pens to Sabrina. In return, Sabrina gave ¹₈ of the total number of pens that she had to Jean. In the end, each girl had the same number of pens. How many pens did Sabrina have at first?

	Sabrina	Jean	Total
Before 1	?	4 u	70
Change 1	+ 1 u	- 1 u
After 1	40	3 u	70
Before 2	8 p	3 u	70
Change 2	- 1 p	+ 1 p
After 2	7 p (35)	35	70

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

Number of pens that Jean and Sabrina each had in the end is the same.

Number of pens that Sabrina had in the end
= 70 ÷ 2
= 35

Number of pens that Sabrina had in the end = 7 p

7 p = 35

1 p = 35 ÷ 7 = 5

Number of pens that Sabrina had after receiving some pens from Jean
= 8 p
= 8 x 5
= 40

Number of pens that Jean had after giving to Sabrina
= 70 - 40
= 30

3 u = 30

1 u = 30 ÷ 3 = 10

Number of pens that Jean had at first
= 4 u
= 4 x 10
= 40

Number of pens that Sabrina had at first
= 70 - 40
= 30

Answer(s): 30