In order to determine the midpoint between the given points, use the following expressions for the x and y coordiantes of the midpoint:
where (x1,y1) and (x2,y2) are the coordinates of the given points.
In this case. you have:
(x1,y1) = (5,-7)
(x2,y2) = (5,7)
Hence, the coordinates of the midpoint is (5,0)