Answer:  28x  + 15y = 131  and x + y =  7  where x is the number of Dress shirt and y is the number of T-shirt.
Step-by-step explanation:
We will represent the number of Dress shirt he bought by x and we will represent the number of T-shirt he bought by y.
We know that he spent 131 so the cost of each dress shirt plus the cost of each T-shirt has to equal  131.  Also, he bought 7 total shirts so x plus y has to equal 7.
28x  + 15y = 131 Â
x + y = Â 7
Note: it says don't solve so I didn't solve but if you want to solve use these equations.