Pamela bought some rings and necklaces for her friends. The price of each ring was $4.10 while the price of each necklace was $12.80. For every 7 necklaces bought, she was given one such ring for free. After receiving the free rings, the number of rings was ¹₃ of the number of necklaces bought. If Pamela paid a total of $1140.80, how much more did she pay for the necklaces than the rings?

Necklaces	Rings
3x7	1x7
Bought	Free	Bought
7x3	1x3
21 u	3 u	4 u

	Necklaces	Rings
	Bought	Free	Bought
Number	21 u	3 u	4 u
Value	$12.80	0	$4.10
Total value	268.8 u	0	16.4 u

The number of necklaces bought is the repeated identity. Make the number of necklaces bought the same.  LCM of 3 and 7 is 21.

Cost of the bought necklaces
= 21 u x 12.80
= 268.8 u

Cost of the bought rings
= 4 u x 4.10  
= 16.4 u

Total cost of the bought items
= 268.8 u + 16.4 u
= 285.2 u

285.2 u = 1140.80

1 u = 1140.80 ÷ 285.20 = 4

Amount that she paid more for the necklaces than the rings
= 268.8 u - 16.4 u 
= 252.4 u
= 252.4 x 4
= $1009.60

Answer(s): $1009.60