At a bird park, each adult ticket cost $23 and each child ticket cost $10. On Friday, the number of adult tickets sold was 200 less than the number of child tickets. On Saturday, the number of adult tickets sold decreased by 10% while the number of child tickets sold increased by 5%. If a total of 600 tickets were sold on Saturday, how much money was collected on Friday?

	Adult tickets	Child tickets	Total tickets
Before	1 u	1 u + 200	2 u + 200
Change	- 0.1 u	+ 0.05 u + 10
After	0.9 u	1.05 u + 210	1.95 u + 210

10% x 1 u = ¹⁰₁₀₀ x 1 u = 0.1 u 
5% x 1 u = ⁵₁₀₀ x 1 u = 0.05 u
5% x 200 = ⁵₁₀₀ x 200 = 10

Number of tickets sold on Saturday
= 0.9 u + 1.05 u + 210
= 1.95 u + 210

1.95 u + 210 = 600
1.95 u = 600 - 210
1.95 u = 390

1 u = 390 ÷ 1.95 = 200

Amount collected from adult tickets on Friday
= 1 u x 23
= 200 x 23
= $4600

Amount collected from child tickets on Friday
= 10(1 u + 200)
= 10(200 + 200)
= 10 x 400
= $4000

Total amount collected on Friday
= 4600 + 4000
= $8600

Answer(s):$8600