In a stationery shop, the number of post-it pads was ¹₃ of the total number of post-it pads and correction tapes together. Jenson sold the post-it pads and correction tapes in sets of 1 post-it pad and 7 correction tapes. After selling all the correction tapes, he still had 10 post-it pads left. How many correction tapes were in the stationery shop at first?

	Post-it Pads	Correction Tapes
Before	1x7 = 7 u	2x7 = 14 u
Change	- 1x2 =  - 2 u	- 7x2 = - 14 u
After	10	0

Since all the correction tapes were sold, the number of correction tapes at first and the number of correction tapes sold were the same.  Make the number of correction tapes at first and sold the same.  LCM of 2 and 7 is 14.

Number of post-it pads sold
= 7 u - 2 u
= 5 u

5 u = 10

1 u = 10 ÷ 5 = 2

Number of correction tapes at first
= 14 u
= 14 x 2
= 28

Answer(s): 28