If the shadow of a x metre tall tree is broken up in the middle and touches the top of the tree on the ground at a particular distance from the ground.calculate the image distance?
Did you draw a diagram? If the height of the stump is h, then the part leaning down to the ground is x-h. So, assuming the tree was originally perpendicular to the ground, the distance d is
h^2+d^2=(x-h)^2
This distance will only equal shadow length if the sun is at the right angle.