This is my answer! I solve it by myself, check it out!!!! Sorry for late
The first shaded triangle is 144 cm.
Answer: approximately 29 feet
Explanation: You need to find a tree so that the angle of elevation from the end of the shadow to top of the tree is 40 degrees.
The length of the shadow is an adjacent side and is 35.
The height of the tree is the opposite side. You could use X.
Tan ratio = opposite/adjacent
tan(40) = x/35
x = 35*tan(40) =29.37