Someone PlzZ help

Using the side-splitter theorem, daniel wrote a proportion for the segment formed by luke segment de. what is ec?

We just started the introduction into circles and i have no idea how to do this.

In the diagram, the ratios of two pairs of corresponding sides are equal to prove that almn - axyz by the sas similarity theorem, it also needs to be shown that x 6 z un z zz un = 2x zləzz lezy