The opera house had 931 seats. There were 25% fewer $45-seats than $20-seats. 75% of the $20-seats and some $45-seats were sold. A total of $30300 was collected. How many seats were unsold?

	$45	$20	Total
Number	3 u	4 u	7 u

100% - 25% = 75%
⁷⁵₁₀₀ = ³₄

Total number of seats
= 3 u + 4 u
= 7 u

7 u = 931

1 u = 931 ÷ 7 = 133

Total number of $20-seat tickets
= 4 u
= 4 x 133
= 532

Number of $20-seat tickets sold
= 75% x 532
= ⁷⁵₁₀₀ x 532
= 399

Amount collected from $20-seat tickets sold
= 399 x 20
= $7980

Amount collected from $45-seat tickets sold
= 30300 - 7980
= $22320

Number of $45-seat tickets sold
= 22320 ÷ 45
= 496

Number of tickets sold
= 399 + 496
= 895

Number of tickets left unsold
= 931 - 895
= 36

Answer(s): 36