Answer:
x = 6.6; DE = 16.6
Step-by-step explanation:
Assume the diagram is like the figure below.
1. Calculate the value of x
In a right triangle, the altitude drawn from the right angle to the hypotenuse divides the triangle into two similar triangles.
Thus, ∆CDF ~ ∆FDE, and
[tex]\begin{array}{rcl}\dfrac{CD}{DF} &=& \dfrac{FD}{DE}\\\\\dfrac{5}{9} &=& \dfrac{9}{2x + 3}\\\\5(2x + 3) & = &81\\10x + 15 & = & 81\\10x & = & 66\\x & = & \mathbf{6.6}\\\end{array}[/tex]
2. Calculate the length of DE
DE = 2x + 3 = 2(6.6) + 3 = 13.2 + 3 = 16.2
