Question 782451
Let n = number of t-shirts.  
2 hours is 120 minutes.


The time to do everything must be no greater than 120 minutes.
Account for all time quantities.
{{{12+36+9n<=120}}}


Once solved for n, you need to pick the nearest whole number which makes sense.  The reason is that the artist must finish a t-shirt that he starts; he cannot paint only a partial picture.