Hey there!
To start, the formula to find the midpoint coordinate pair of two given coordinates is as follows:
(

,

)
Knowing this, plug in your given values (the two x values are -6 and 4; the two y values are 5 and -7) and simplify:
(

,

)
=(

,

)
=(-1,-1)
Therefore, the midpoint of the coordinates (-6,5) and (4,-7) would be (-1,-1).
Hope this helps and have a marvelous day! :)