At a concert hall, each adult ticket cost $26 and each child ticket cost $17. On Monday, the number of adult tickets sold was 120 less than the number of child tickets. On Tuesday, the number of adult tickets sold decreased by 30% while the number of child tickets sold increased by 25%. If a total of 345 tickets were sold on Tuesday, how much money was collected on Monday?

	Adult tickets	Child tickets	Total tickets
Before	1 u	1 u + 120	2 u + 120
Change	- 0.3 u	+ 0.25 u + 30
After	0.7 u	1.25 u + 150	1.95 u + 150

30% x 1 u = ³⁰₁₀₀ x 1 u = 0.3 u 
25% x 1 u = ²⁵₁₀₀ x 1 u = 0.25 u
25% x 120 = ²⁵₁₀₀ x 120 = 30

Number of tickets sold on Tuesday
= 0.7 u + 1.25 u + 150
= 1.95 u + 150

1.95 u + 150 = 345
1.95 u = 345 - 150
1.95 u = 195

1 u = 195 ÷ 1.95 = 100

Amount collected from adult tickets on Monday
= 1 u x 26
= 100 x 26
= $2600

Amount collected from child tickets on Monday
= 17(1 u + 120)
= 17(100 + 120)
= 17 x 220
= $3740

Total amount collected on Monday
= 2600 + 3740
= $6340

Answer(s):$6340