Mark M. answered 02/16/15
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Retired Math prof with teaching and tutoring experience in trig.
1. Let x = number of football games or dances
If C1 = cost of x games in a month, then
C1 = 30 + 2.5x
If C2 = cost of x classes in a month, then
C2 = 42 + x
2. Cost of 5 games = 30 + 2.5(5) =$42.50
Cost of 5 classes = 42 + 5 = $47
3. The costs are the same if 30 + 2.5x = 42 + x
1.5x = 12
x = 8
4. When x = 8, C1 = 30 + 2.5(8) = $50
C2 = 42 + 8 = $50
The graphs intersect at the point (8, 50). This is the point at which the monthly costs are the same.