We know that
• Adult tickets cost $18.00 each.
,
• Children's tickets cost $10.00 each.
,
• The total is $960.00.
,
• There were sold 64 tickets.
First, we define the equation for the total money earned one evening.

Where x is adult tickets, and y is children's tickets.
Now, we defined the equation for the total number of tickets.

We isolate x in the second equation.

Then, we replace this last equation in the first one to solve for y.

There were sold 24 children tickets.
Now we find the number of adult tickets.

Therefore, there were sold 40 adult tickets.