If all the shirts are the same your answer should be 5^3
If all the shirts are different your answer should be 5*4*3
Because if you think about it like this... (i'm assuming all the shirts are different)
The first hanger, we have a choice of 5, the second one we lost 1 shirt hence we have from a choice of 4 and on the 3rd hanger we have 3 shirts left...
hence 5*4*3 choices