Question 101803
Let A = cost of adult ticket and C = cost of child's ticket.
We can write:
7A+2C = 172 but C = A-4, substituting this, we get:
7A+2(A-4) = 172 Simplify and solve for A.
7A+2A-8 = 172
9A-8 = 172  Add 8 to both sides.
9A = 180 Divide both sides by 9.
A = $20 This is the cost of an adult ticket.
C = A-4
C = $20-$4
C = $16  This is the cost of a child's ticket.