The auditorium had 875 seats. There were 25% fewer $30-seats than $10-seats. 60% of the $10-seats and some $30-seats were sold. A total of $14130 was collected. How many seats were unsold?

	$30	$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 = 875

1 u = 875 ÷ 7 = 125

Total number of $10-seat tickets
= 4 u
= 4 x 125
= 500

Number of $10-seat tickets sold
= 60% x 500
= ⁶⁰₁₀₀ x 500
= 300

Amount collected from $10-seat tickets sold
= 300 x 10
= $3000

Amount collected from $30-seat tickets sold
= 14130 - 3000
= $11130

Number of $30-seat tickets sold
= 11130 ÷ 30
= 371

Number of tickets sold
= 300 + 371
= 671

Number of tickets left unsold
= 875 - 671
= 204

Answer(s): 204