Kristin spent $131 on shirts. Fancy shirts cost $28 and plain shirts cost $15. If she bought a total of 7 then how many of each kind did she buy?
Let x be the number of fancy shirts Kristin bought.
So the number of plain shirts she bought is 7 - x.
The total cost for the fancy shirts is 28x dollars.
The total cost for the plain shirts is 15(7 - x) = 105 - 15x dollars.
The total cost is 28x + 105 - 15x = 131 dollars.
Combining like terms, we get 13x + 105 = 131.
Subtracting 105 from both sides, we get 13x = 131 - 105 = 26.
Dividing both sides by 13, we get x = 2.
Thus, Kristin bought 2 fancy shirts and 7 - 2 = <<7-2=5>>5 plain shirts. Answer: \boxed{2}.