8) it costs a band $8 per t-shirt produced. at a small festival the band gives away 10 t-shirts, and sells others for $20 each. their total t-shirt-related profits (taking into account those they gave away) is $304, how many t-shirts did the band sell?

If the t-shirts cost $8 to make, and the band sells them for 20$ they make a profit of $12 a shirt. 

if after the concert, their profit is 304$ then I believe the way to solve it would be 304/12 which equals 25.3
However, they did not make a profit off of the 10 shirts that they gave away. 10*12 equals 120
304-120 equals 184 
184/12 equals 15. 
Your answer should be either 25 or 15

The correct answer is d. (0,5)

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