Question 592994
The whole pie would be the amount you started with
Draw a line through the center and label half of the 
pie as "parking"
Now divide the other 1/2 of a pie into 2 equal parts
Label 1/2 as "tickets"
Label the other half as $18
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Now you can see that "tickets" has to
equal $18 also, and "parking" must be
$18 + $18 = $36
So, the whole pie is $18 + $18 + $36 = $72
which is what you started with.