The drama centre had 1908 seats. There were 20% fewer $50-seats than $15-seats. 80% of the $15-seats and some $50-seats were sold. A total of $30770 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 = 1908

1 u = 1908 ÷ 9 = 212

Total number of $15-seat tickets
= 5 u
= 5 x 212
= 1060

Number of $15-seat tickets sold
= 80% x 1060
= ⁸⁰₁₀₀ x 1060
= 848

Amount collected from $15-seat tickets sold
= 848 x 15
= $12720

Amount collected from $50-seat tickets sold
= 30770 - 12720
= $18050

Number of $50-seat tickets sold
= 18050 ÷ 50
= 361

Number of tickets sold
= 848 + 361
= 1209

Number of tickets left unsold
= 1908 - 1209
= 699

Answer(s): 699