At a theme park, each adult ticket cost $23 and each child ticket cost $9. On Friday, the number of adult tickets sold was 120 less than the number of child tickets. On Saturday, the number of adult tickets sold decreased by 40% while the number of child tickets sold increased by 10%. If a total of 812 tickets were sold on Saturday, how much money was collected on Friday?

	Adult tickets	Child tickets	Total tickets
Before	1 u	1 u + 120	2 u + 120
Change	- 0.4 u	+ 0.1 u + 12
After	0.6 u	1.1 u + 132	1.7 u + 132

40% x 1 u = ⁴⁰₁₀₀ x 1 u = 0.4 u 
10% x 1 u = ¹⁰₁₀₀ x 1 u = 0.1 u
10% x 120 = ¹⁰₁₀₀ x 120 = 12

Number of tickets sold on Saturday
= 0.6 u + 1.1 u + 132
= 1.7 u + 132

1.7 u + 132 = 812
1.7 u = 812 - 132
1.7 u = 680

1 u = 680 ÷ 1.7 = 400

Amount collected from adult tickets on Friday
= 1 u x 23
= 400 x 23
= $9200

Amount collected from child tickets on Friday
= 9(1 u + 120)
= 9(400 + 120)
= 9 x 520
= $4680

Total amount collected on Friday
= 9200 + 4680
= $13880

Answer(s):$13880