OH MY GOD, YOU'RE AWESOME!!!!
Thank you very much!! I'll follow your brilliant instructions!

Well, I'm a noob with inkscape, can you please tell me how to do that? thank you very much.

I selected just these 2 objects (individually grouped). This is the file, if you want to see they are actually grouped.

Same thing happened to me but I duplicated my draw and nothing happen. I have a logo, I duplicate it and I move it (with transform tool). Everything is ok, but now I want to interpolate them, so I select 'em and I use the Interpolation tool as this tutorial says: Exponent to 1, Interpolation steps t...

Exactly, thank you very much but, why grouped couldn't I erase it?

First thing: I'm new on Inkscape. Second Thing: please, excuse my engish, I'm working on it, but I know my grammar is so bad, I invite you to correct me if you see I writte a mistake. Ok, my error is that I can't erase the world symbol from Iceweasel, but I don't know why. The error in english says ...