did i need to write everything down or there is easier way ?

Yes :) i found 25:2=12.5 it is mean that it passes through a point deviding it into two parts i drawed a vertical line through 251 and 39000 and the horizontal throug 245 and 37000 intersection point is 251 and 37000 (D). Thanks Melody ! :)

Mmm

Well there are far more dots to the right of 244 ft than to the left so that is not a median height.

    So it is not either of the first two

39000f^3 has lots more dots below than above so its not the last one

That leaves you with C or d.

Just count the dots.  There has to be the same number above as below 

and

the same number on the left as on the right.  :)

It is a good question :)