Answer :

When you rotate a coordinate pair by 180 degrees you simply multiply the x and the y by a negative 1

so 3 x -1 and -5 x -1 will give you a new coordinate pair of (-3, 5)

hope this helps
if it was rotated 180, then the  siigns are switched becasue 180 is 1/2 of 360, so the signs are switched and you get (-3,5)

this was kind of easy so maybe I am wrong.