In the diagram, $ABCD$ is a rectangle, and $E$ is in the interior of the rectangle, find $DE$

Question

How would I start this type of problem?

Answer 1

Pythagorean theorem will give you $PE$ and $EQ$ in term of $x.$ Applied again you can find $y$ and again for $DE.$ And if you are lucky, the $x$ drops out along the way.