So if triangle ABC is similiar to triangle DEC then we know that when two figures are similar, the ratios of the lengths of their corresponding sides are equal.So we can write:
AC/DC = BC/EC =AB/DE = k
BC= 9ft + 6ft = 15
BC/EC= k
15/6=k
Now that we know the k we can find the height of the tree that's equal to AB:
AB/DE= k
AB/4=15/6
6AB= 15 x 4
AB= 60/6 = 10
The height of the tree is 10ft
