Find the coordinates of the other endpoint of the segment, givern its midpoint (3,-5) and one endpoint (-5,4)
(-5,4) - (3,-5) = (-8,9)
So, you add (-8.9) to the midpoint to get to (-5,4)
So, subtract (-8,9) to get to the other endpoint:
(3,-5)-(-8,9) = (11,-14)