Answer:
We have to prove the triangles ΔXYW and ΔZYW are similar. We can do this by showing that they have two equal/in-ratio corresponding sides with the same angle between them (SAS/side-angle-side), or by showing they have two equal corresponding angles (AA/angel-angle), or by showing their sides are in ratio (SSS).
We are told XY=ZY, so we already know the triangles share an equal side.
Both triangles also share YW as a side.
Because YW bisects <XYZ, we know <XYW = <ZYW, so we know the angle between the triangle's corresponding sides are the same.
Therefore, since the triangles have two equal corresponding sides with the same angle between them (SAS), we can say they are similar.
Hope this helps :)