Here we're dealing in two dimensions and thus need a separate midpoint equation for each variable, x and y. First, take the average of the x-coordinates of these two given points: (8-10)/2, or -1. This is the desired x-coordinate of the midpoint. Next, take the average of the y-coordinates of these two points: (-10-8)/2, or -9.
Then the midpoint of the line segment joining the two given points is (-1,-9).