You can
put this solution on YOUR website!C-Child
A-Adult
1.

Total tickets sold.
2.

Total tickets cost.
Use eq. 1 to solve for A as a function of C.
1.

Substitute this expression for A in eq. 2,
2.

Solve for C.

Use eq. 1 to solve for A.

9 adult and 21 children tickets were sold.