The height of the tree is the sum of the part below the line parallel to the horizontal and the part above the line parallel to the horizontal.
Height of the part below the line parallel to the horizontal = 18 sin16° = 4.96 meters Horizontal distance of the tip of the of the shadow from the tree = 18 cos16° = 17.30 meters Height of the part above the line parallel to the horizontal = 17.3 tan68° = 42.83 meters