-5/6=(8,4)(x,y)
-5/6=y-4/x-8
6y-24=-5x+40
6y=-5x/6+64/6
Y=-5x/6+64/6
51 ft is the answer
Explanation
The hight of the man divided by the hight of school ( which is unknown )
Equal
The length of the shadow of the man divided by the shadow of the school
Cross multiplication and find the value of unknown x which is 51... and ya