On Friday, 690 more men than women attended a concert. On Saturday, the number of men decreased by 50% and the number of women increased by 80%. 621 audience attended the concert on Saturday. If each ticket cost $8, how much money was collected from the sale of concert tickets on Friday?

	Men		Women
Comparing between the men and the women at first	690 more
Before	2x5	+ 690	5x2
Change	- 1x5	- 345	+ 4x2
After	1x5	+ 345	9x2

	Men		Women
Before	10 u + 690		10 u
Change	- 5 u - 345		+ 8 u
After	5 u + 345		18 u

50% = ⁵⁰₁₀₀ = ¹₂

80% = ⁸⁰₁₀₀ = ⁴₅

50% x 690
= ⁵⁰₁₀₀ x 690
= 345

690 - 345 = 345

Total number of tickets sold on Saturday 
= 5 u + 345 + 18 u
= 23 u + 345 

23 u + 345 = 621
23 u = 621 - 345
23 u = 276

1 u = 276 ÷ 23 = 12

Total number of tickets sold on Friday
= 10 u + 690 + 10 u 
= 20 u + 690
= 20 x 12 + 345
= 585

Amount collected from the sale of concert tickets on Friday
= 585 x 8
= $4680

Answer(s): $4680