Geometry – Similar Polygons

https://static.k12.com/eli/bb/348/1_24092/1_45176_4_24096/7267202f644a91fd1d811ad92275b1111f35f1ab/media/3cec4343581b22182e4f81d5e0cfae5c668ee0c0/89143.PDF What’s the ration I use? They used 3/23 for the example but I don’t know how they got that.