You can indeed use similar triangles to get a side of another similar triangle.
let's say Edwardo stood next to the building and his shadow was 20ft, he's 4ft tall, and the building cast a shadow of 125ft, then, check the picture below.
let's say Edwardo stood next to the building and his shadow was 20ft, he's 4ft tall, and the building cast a shadow of 125ft, then, check the picture below.