what do i do. i dont understand

Question

on the first day of ticket sales the school sold 3 senior citizen and 9 children tickets for a total of 75. the school took in 67 on the second day by selling 8 senior citizens and 5 child tickets. what is the price on each of one senior citizen and one child ticket?

Answer 1

x = cost of senior tickets

y = cost of children's tickets

can create two equations in two unknowns

3x + 9y = 75

8x + 5y = 67

multiply top equation by 8 and bottom equation by 3:

24x + 72y = 600

24x + 15y = 201

subtract 2nd equation from the first

57y = 399

y = 7

plug y = 7 into first equation to solve for x:

3x + 9y = 75

3x + 9(7) = 75

3x = 12

x = 4

senior ticket is $4 and children's ticket is $7