Since the coordinates of m and r are not given, therefore, I cannot give an exact answer. However, I will help you with the concept
Suppose that we are given two points (
The midpoint can be calculated as follows:x-coordinate of midpoint =

y-coordinate of midpoint =

Therefore, all you have to do to get the midpoint of MR is substitute with the coordinates of M (

and R (

in the above formula.
Hope this helps :)