The theatre had 1692 seats. There were 20% fewer $50-seats than $15-seats. 60% of the $15-seats and some $50-seats were sold. A total of $31610 was collected. How many seats were unsold?

	$50	$15	Total
Number	4 u	5 u	9 u

100% - 20% = 80%
⁸⁰₁₀₀ = ⁴₅

Total number of seats
= 4 u + 5 u
= 9 u

9 u = 1692

1 u = 1692 ÷ 9 = 188

Total number of $15-seat tickets
= 5 u
= 5 x 188
= 940

Number of $15-seat tickets sold
= 60% x 940
= ⁶⁰₁₀₀ x 940
= 564

Amount collected from $15-seat tickets sold
= 564 x 15
= $8460

Amount collected from $50-seat tickets sold
= 31610 - 8460
= $23150

Number of $50-seat tickets sold
= 23150 ÷ 50
= 463

Number of tickets sold
= 564 + 463
= 1027

Number of tickets left unsold
= 1692 - 1027
= 665

Answer(s): 665