The drama centre had 2412 seats. There were 20% fewer $25-seats than $10-seats. 75% of the $10-seats and some $25-seats were sold. A total of $20675 was collected. How many seats were unsold?

	$25	$10	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 = 2412

1 u = 2412 ÷ 9 = 268

Total number of $10-seat tickets
= 5 u
= 5 x 268
= 1340

Number of $10-seat tickets sold
= 75% x 1340
= ⁷⁵₁₀₀ x 1340
= 1005

Amount collected from $10-seat tickets sold
= 1005 x 10
= $10050

Amount collected from $25-seat tickets sold
= 20675 - 10050
= $10625

Number of $25-seat tickets sold
= 10625 ÷ 25
= 425

Number of tickets sold
= 1005 + 425
= 1430

Number of tickets left unsold
= 2412 - 1430
= 982

Answer(s): 982