Hi Lemonie,
When you say you want to "cut out" the 1966, do you want the result to be the 1966 all by itself? Or do you want the tennis ball with the 1966 transparent? Either way, it should be fairly simple here, because the tennis ball and the text are already separate. You just need to delete the part that you don't want.
Ah-ha! From your need to add perspective, it seems like you want the 1966 by itself. So just delete the tennis ball

There may be a couple of different ways to add perspective, and it depends on you goals. In addition to the Perspective extension that you've been trying to use, there's also the Envelope Deformation extension and also an Env. Deform. path effect (Path menu > Path effect editor). I love using the live path effect, but the envelope deformation tools don't add true perpective, but more of a simulation of perspective. I suppose you might also be able to simulate perspective using skewing, but I wouldn't advise it.
With the Perspective extension, you have to draw the skeleton path in one way, and one way only -- clockwise starting in the bottom left corner (
http://tavmjong.free.fr/INKSCAPE/MANUAL ... erspective). Also, you have to select the text first, then the skeleton path.
I also noticed that you have some other text in the file, that can't be seen. Some of it is white, which is why you can't see it. The other text is black, and appears to be fully opaque. I can't figure out why it can't be seen. But anyway, I just wanted to mention it, and depending on what you'll be doing with the final product, you might want to just delete it. Perhaps you've disguised it just to show us a simple file for troubleshooting, but I wanted to mention it just in case.
Let us know how it goes
