I'm not sure about this, and I don't know if it's right. It should be when you need an accurate answer.
3. The conditions of this question are not clear, so I am not very good at it. sorry
I did all the above by myself. I can't guarantee the accuracy I'm sorry
4: There are one sixth and one fifth.
5. This needs to be used as an auxiliary line to prove that two opposite triangles are similar. If x is set, you probably won't know. Plus there are no letters on your map, which is not easy to do.