Question 101783
Ok first lets set the adult ticket price equal to x
adult ticket price = x
Now define the cost of a child's ticket in terms of x
Given: child's ticket is $4 less than cost of an adult ticket
child ticket price = x-4
Ok now lets look at what else the problem tells us
Given: 7 adult tickets and 2 child tickets cost a total of $172
so what does this tell us?
7 times the cost of an adult ticket plus 2 times the cost of a child's ticket equals $172
Now remembering that we have already stated that adult ticket price = x
and child ticket price = x-4 
we can write an equation to solve for x
7(adult ticket price) + 2(child ticket price) = 172
7x + 2(x-4) = 172
7x + 2x -8 = 172
9x -8 = 172
9x = 180
x = 20
<b>Answer: Adult ticket price is $20.00</b>
Now we can use this to find the child's ticket price
child ticket price = x-4
child ticket price = 20-4
child ticket price = 16
<b>Answer: Child ticket price is $16.00</b>
Check both answers in the orginal equation
7(adult ticket price) + 2(child ticket price) = 172
7(20) + 2(16) = 172
140 + 32 = 172
172 = 172