We know that
• They sold $1470 worth of tickets.
,
• A child ticket costs $7.75.
,
• An adult ticket costs $10.25.
Le's call x children tickets, and y adults tickets. Using the given information, we can express the following. (a)

On the other hand, if the cinema sold 75 children's tickets, then we can solve the equation for y.

Hence they sold 86 adult tickets.