so the fliping over the y-axis you would count how many spaces it is to the y-axis then count that many on the other side do the same with all three points. for the x-axis do the same as you did for y. for rotating it 90 degrees clockwise you would flip the numbers of your coordinates other points and swap the x sign
example: -5,-6 it is now -6,5 or if you had -4,6 it is now 6,4