We have 2 types of tickets, A tickets and B tickets. The total number of tickets sold was 500, so an equation for this NUMBER of tickets is A + B = 500. The MONEY equation is something different. A tickets cost 10, so they are represented by 10A; B tickets cost 60, so they are represented by 60B. The total dollar sales for A and B are 6000. Our money equation for the sales is 10A + 60B = 6000. Solve the first equation for A: A = 500 - B. Sub that value for A into the second equation to solve for B: 10(500-B) + 60B = 6000. Distribute through the parenthesis to get 5000 - 10B + 60B = 6000. Combine like terms to get 50B = 1000. B = 20. There were 20 type B tickets sold. A = 500 - B, so A = 500 - 20 and A = 480. There were 480 type A tickets sold.