Another similar triangles problem... Woo hoo. This one was way more bizarre than any other, and is exactly why I have difficulty with these problems. For some reason, the problem expects me to have some inherent intuition and automatically know I'm supposed to flip the problem randomly, and gives absolutely no explanation as to why. Cosine (CAH) is Adjacent over Hypotenuse. For whatever reason, they flipped it, making it Hypotenuse over Adjacent, and didn't explain in the steps why. This is why I am having a hard time learning similar triangles. There's obviously a hidden step I'm missing because it isn't being explained, just done.