Jen has 30% as many pens as Tiffany. Tiffany has 140% as many pens as Zara. If Tiffany gives 90 pens to Zara, both will then have an equal number of pens. Find the average number of pens the three of them have.

Jen	Tiffany	Zara
3x7	10x7
	7x10	5x10
21 u	70 u	50 u

30% = ³⁰₁₀₀ = ³₁₀
140% = ¹⁴⁰₁₀₀= ⁷₅

The number of pens that Jen has is repeated.  Make the number of pens that Jen has the same. LCM of 10 and 7 is 70.

	Tiffany	Zara	Total
Before	70 u	50 u	120 u
Change	- 10 u	+ 10 u
After	60 u	60 u	120 u

Total number of pens that Tiffany and Zara have
= 70 u + 50 u
= 120 u

After Tiffany gives to Zara, both of them will have the same number of pens. 

The total number of pens that Tiffany and Zara have remains unchanged.

Number of pens that each of them will have
= 120 u ÷ 2
= 60 u

Number of pens that Tiffany gives to Zara
= 70 u - 60 u
= 10 u

10 u = 90

1 u = 90 ÷ 10 = 9

Total number of pens that three of them have
= 120 u + 21 u
= 141 u

Average number of pens that each of them have
= 141 u ÷ 3
= 47 u
= 47 x 9
= 423

Answer(s): 423