The concert hall tickets are priced at $15 and $12.  The number of $15-dollar tickets available is  1³₄ that of the number of $12-dollar tickets. 2 out of 3 of the $15-dollar tickets and all the $12-dollar tickets were sold. The ticket sales amounted to $3894. How much more would have been collected if all the tickets were sold?

	$15	$12
Comparing $15 and $12 tickets at first	7x3 = 21 u	4x3 = 12 u
Before	3x7 = 21 u
Change	- 2x7 = - 14 u	- 12 u
After	1x7 = 7 u	0 u

The number of 15 tickets at first is repeated.  Make the number of 15 tickets the same.  LCM of 3 and 7 is 21.

1³₄ = ⁷₄

Number of $15 tickets : $12 tickets = 7 : 4

	$15	$12	Total
Number	14 u	12 u
Value	$15	$12
Total value	210 u	144 u	$3894

Total amount collected from the sale of the sold tickets
= 210 u + 144 u
= 354 u

1 u = 3894 ÷ 354 = 11

Number of $15-tickets left unsold
= 7 u 
= 7 x 11
= 77

More amount to be collected if all the tickets were sold
= 77 x 15
= $1155

Answer(s): $1155