15.2 Midpoint formula: $M = ( \frac{x_1+x_2}2 ,\frac{y_1+y_2}2)$
Midpoint formula: $M = ( \frac{x_1+x_2}2 ,\frac{y_1+y_2}2)$
When given the end points of a line segment, you can find out its midpoint by using the midpoint formula. As the name might have already suggested, midpoint is basically the halfway between two end points. All you need to do is dividing the sum of xvalues and the sum of yvalues by 2. This formula also comes in very handy when you are asked to find the point of intersection or equation of a perpendicular bisector of a given line segment.
Basic concepts:
 Draw on coordinate planes
 Horizontal and vertical distances
Lessons

1.
Determine the midpoint of the line segment with the given endpoints.

2.
Determine the missing x.