Yen bought some necklaces and rings for her friends. The price of each necklace was $3.70 while the price of each ring was $13.90. For every 7 rings bought, she was given one such necklace for free. After receiving the free necklaces, the number of necklaces was ¹₃ of the number of rings bought. If Yen paid a total of $2146.90, how much more did she pay for the rings than the necklaces?

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

	Rings	Necklaces
	Bought	Free	Bought
Number	21 u	3 u	4 u
Value	$13.90	0	$3.70
Total value	291.9 u	0	14.8 u

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

Cost of the bought rings
= 21 u x 13.90
= 291.9 u

Cost of the bought necklaces
= 4 u x 3.70  
= 14.8 u

Total cost of the bought items
= 291.9 u + 14.8 u
= 306.7 u

306.7 u = 2146.90

1 u = 2146.90 ÷ 306.70 = 7

Amount that she paid more for the rings than the necklaces
= 291.9 u - 14.8 u 
= 277.1 u
= 277.1 x 7
= $1939.70

Answer(s): $1939.70