The stadium tickets are priced at $21 and $12.  The number of $21-dollar tickets available is  2¹₃ that of the number of $12-dollar tickets. 2 out of 5 of the $21-dollar tickets and all the $12-dollar tickets were sold. The ticket sales amounted to $1422. How much more would have been collected if all the tickets were sold?

	$21	$12
Comparing $21 and $12 tickets at first	7x5 = 35 u	3x5 = 15 u
Before	5x7 = 35 u
Change	- 2x7 = - 14 u	- 15 u
After	3x7 = 21 u	0 u

The number of 21 tickets at first is repeated.  Make the number of 21 tickets the same.  LCM of 5 and 7 is 35.

2¹₃ = ⁷₃

Number of $21 tickets : $12 tickets = 7 : 3

	$21	$12	Total
Number	14 u	15 u
Value	$21	$12
Total value	294 u	180 u	$1422

Total amount collected from the sale of the sold tickets
= 294 u + 180 u
= 474 u

1 u = 1422 ÷ 474 = 3

Number of $21-tickets left unsold
= 21 u 
= 21 x 3
= 63

More amount to be collected if all the tickets were sold
= 63 x 21
= $1323

Answer(s): $1323