Andy wants to find the distance across a river. In
order to find the distance CD, Andy stands at point
D, directly across from point C, and walks 200 feet
to the left, placing a marker at a point E. Andy
continues walking another 300 feet to point A, and
then follows the path to the left, walking until the
markers at points and C line up. Andy marks this
location B and measures AB. What is CD?