Hello, sri340!
In quadrilateral $\displaystyle ABCD\!:\;\;AB=5,\;BC=8,\;CD = 20.$
$\displaystyle \angle B \,=\,\angle C \,=\,90^o$
What is length of segment $\displaystyle AD$ ?
Answer was 17 units.
My answer was different . . . how ?
It's hard to see your work from here . . .
. . But it looks like you played the $\displaystyle {\color{blue}J\heartsuit}$ instead of the $\displaystyle {\color{blue}3\clubsuit}$ Code:
A 5 B
* - - - *
* : |
* : |
* :8 |8
* : |
* : |
D * - - - - - + - - - * C
: 15 E 5 :
: - - - - 20 - - - :
In right triangle $\displaystyle AED$, use Pythagorus:
. . . $\displaystyle AD^2 \;=\;DE^2 + AE^2$