There are many ways to answer this. Here is one answer shown below
AB/WX = BC/XY
On the left side is the ratio of AB over WX. These two sides are the bottom horizontal portions of the triangles. This is a visual indication that they correspond to one another. More concrete proof of this is that AB and WX are the first two letters of the sequences ABC and WXY respectively. The order is very important to help establish pairs like this.
On the right side of that equation above, we have BC and XY as the diagonal sides on the right part of each triangle. They are the last two letters of ABC and WXY respectively, which is a non-visual way to prove these two sides correspond.
It might help to line up ABC over top WXY so you can pick out the corresponding sides. I show this in the attached image below.
