Answer:
29
Step-by-step explanation:
Let x represent the length of DE. Then ...
AB = x
AD = AB -BD = x - 9
__
AC = x
AE = AC -CE = x - 8
And the Pythagorean theorem applied to triangle ADE tells us ...
x^2 = (x -9)^2 +(x -8)^2
0 = x^2 -34x +145 = (x -5)(x -29)
Solutions are the values of x that make a factor zero: 5 or 29.
The length of DE must be greater than 9, so the appropriate solution from the above equation is x = 29.
The length of DE is 29.
