The auditorium had 880 seats. There were 40% fewer $30-seats than $5-seats. 50% of the $5-seats and some $30-seats were sold. A total of $15175 was collected. How many seats were unsold?

	$30	$5	Total
Number	3 u	5 u	8 u

100% - 40% = 60%
⁶⁰₁₀₀ = ³₅

Total number of seats
= 3 u + 5 u
= 8 u

8 u = 880

1 u = 880 ÷ 8 = 110

Total number of $5-seat tickets
= 5 u
= 5 x 110
= 550

Number of $5-seat tickets sold
= 50% x 550
= ⁵⁰₁₀₀ x 550
= 275

Amount collected from $5-seat tickets sold
= 275 x 5
= $1375

Amount collected from $30-seat tickets sold
= 15175 - 1375
= $13800

Number of $30-seat tickets sold
= 13800 ÷ 30
= 460

Number of tickets sold
= 275 + 460
= 735

Number of tickets left unsold
= 880 - 735
= 145

Answer(s): 145