The auditorium had 1603 seats. There were 25% fewer $25-seats than $10-seats. 50% of the $10-seats and some $25-seats were sold. A total of $15930 was collected. How many seats were unsold?

	$25	$10	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 = 1603

1 u = 1603 ÷ 7 = 229

Total number of $10-seat tickets
= 4 u
= 4 x 229
= 916

Number of $10-seat tickets sold
= 50% x 916
= ⁵⁰₁₀₀ x 916
= 458

Amount collected from $10-seat tickets sold
= 458 x 10
= $4580

Amount collected from $25-seat tickets sold
= 15930 - 4580
= $11350

Number of $25-seat tickets sold
= 11350 ÷ 25
= 454

Number of tickets sold
= 458 + 454
= 912

Number of tickets left unsold
= 1603 - 912
= 691

Answer(s): 691