Let x be the number of $30 tickets sold and y be the number of $40 tickets sold:
- there were 65 tickets sold in all: x + y = 65
- total amount paid for them was $2300: 30x + 40y = 2300
x + y = 65
30x + 40y = 2300
From the first equation, y = 65 - x. Substitute into the second equation:
30x + 40y = 2300
30x + 40(65-x) = 2300
Solve for x, the number of $30 tickets sold. Once you have x, y = 65 - x.