1. A scientist would be able to tell the age of a tree by looking at its rings because the rings are the years that the tree has been there. Say for instance if you cut a tree down and you look at the middle you'll see a lot of light colored circles and for every line, it is a year.
2. This would be useful to scientist because besides rocks it also dates earths history.
3. I think this is an example of relative dating because of how the circle are in the tree and it looks like they are in order.