What is the answer and how to get it

Your answer would be A (-8,20). Why because in order to get a mid point you need the equation which is (x + x / 2 , y + y / 2) and if you plug in the numbers (-8,20) and (0,-10) you will end up with the midpoint which is (-4,5), Your welcome.

Mid point formula says
M = X1+X2/2 ; Y1+Y2/2
X1+0/2=-4 Y1+(-10)/2=5
X1=-4x2 Y1-10=5x2
X1=-8 Y1=10+10=20
That means your answer is
A- point R is (-8:20)
Hope this helped