ANSWER
$28
EXPLANATION
The profit function is given as:

where x is the price of the T-shirt in dollars.
To find the profit on a T-shirt whose price is $15, we substitute x=15 into the function and simplify.

We simplify to get:



4/7 = 8/14 = 12/21 = 16/28, etc
y = ( x + 9 )^2 - 2
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