At a point A due South of the building the angle of elevation from the ground to the top of the building is 58ﾟ. At a point B on level ground with a 80 m due West of a the angle of elevation to the top of the building is 27ﾟ. Find the height of the building.

for finding the midpoint of any given 2 pair of points simply add the respective x coordinates with other x coordinate and the y coordinate with other y coordinate and divide them by 2

in your question it will be :

(3+1)/2 for the x coordinate of mid point i.e 2

[8+(-4)]/2 for the y coordinate of midpoint i.e 2

so coordinates of mid point of points (3,8) and (1,-4) will be (2,2)