The concert hall tickets are priced at $13 and $7.  The number of $13-dollar tickets available is  1²₃ that of the number of $7-dollar tickets. 3 out of 7 of the $13-dollar tickets and all the $7-dollar tickets were sold. The ticket sales amounted to $2052. How much more would have been collected if all the tickets were sold?

	$13	$7
Comparing $13 and $7 tickets at first	5x7 = 35 u	3x7 = 21 u
Before	7x5 = 35 u
Change	- 3x5 = - 15 u	- 21 u
After	4x5 = 20 u	0 u

The number of 13 tickets at first is repeated.  Make the number of 13 tickets the same.  LCM of 7 and 5 is 35.

1²₃ = ⁵₃

Number of $13 tickets : $7 tickets = 5 : 3

	$13	$7	Total
Number	15 u	21 u
Value	$13	$7
Total value	195 u	147 u	$2052

Total amount collected from the sale of the sold tickets
= 195 u + 147 u
= 342 u

1 u = 2052 ÷ 342 = 6

Number of $13-tickets left unsold
= 20 u 
= 20 x 6
= 120

More amount to be collected if all the tickets were sold
= 120 x 13
= $1560

Answer(s): $1560