Answer:
B. 6 shirts for $81
Explanation:
When calculating the unit rate in scenarios like this, you have to divide the money by the product. That is because you are splitting the money, not the product itself. You can easily eliminate C and D by knowing the 12x12 multiplication table. A is not the answer because 53/4 = 13.25. The only answer left is B, and 81/6 = 13.50