We are given mid-point (-11, 18).
One end point (-5, 10).

Let us take coordinate of other end points is (x,y).
Therefore,


Given mid point (-11, 18).
Therefore,

and

Multiplying both sides by 2 in both equations, we get
x-5 = -22 and y+10 =36.
x = -22+5 and y = 36-10
x = -17 and y = 26.
Therefore, corrdinates of other end point is (-17, 26).