To find midpoints we have to add both x coordinates and divide by 2, same with e y coordinates:
(x,y)
Midpoint = [(x1+x2)/2 , (y1+y2)/2]
Since:
(x1,y1) = (4,7)
(x2,y2)= (-4,-3)
Midx = 4+(-4) /2 = 0
midy = (7+3)/2=10/2 =5
Midpoints = (0,5)