The opera house had 2556 seats. There were 20% fewer $25-seats than $20-seats. 50% of the $20-seats and some $25-seats were sold. A total of $23475 was collected. How many seats were unsold?

	$25	$20	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 = 2556

1 u = 2556 ÷ 9 = 284

Total number of $20-seat tickets
= 5 u
= 5 x 284
= 1420

Number of $20-seat tickets sold
= 50% x 1420
= ⁵⁰₁₀₀ x 1420
= 710

Amount collected from $20-seat tickets sold
= 710 x 20
= $14200

Amount collected from $25-seat tickets sold
= 23475 - 14200
= $9275

Number of $25-seat tickets sold
= 9275 ÷ 25
= 371

Number of tickets sold
= 710 + 371
= 1081

Number of tickets left unsold
= 2556 - 1081
= 1475

Answer(s): 1475