The opera house had 2133 seats. There were 20% fewer $25-seats than $15-seats. 80% of the $15-seats and some $25-seats were sold. A total of $25220 was collected. How many seats were unsold?

	$25	$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 = 2133

1 u = 2133 ÷ 9 = 237

Total number of $15-seat tickets
= 5 u
= 5 x 237
= 1185

Number of $15-seat tickets sold
= 80% x 1185
= ⁸⁰₁₀₀ x 1185
= 948

Amount collected from $15-seat tickets sold
= 948 x 15
= $14220

Amount collected from $25-seat tickets sold
= 25220 - 14220
= $11000

Number of $25-seat tickets sold
= 11000 ÷ 25
= 440

Number of tickets sold
= 948 + 440
= 1388

Number of tickets left unsold
= 2133 - 1388
= 745

Answer(s): 745