they could be:
1. jealous (most common case)
2. amazed (but not wanting to show it)
3. annoyed of the noise
4. think you're a nerd that they have the right to pick on
5. They are thinking, "IF HEZ CAN SOVEZ DEM CUBIX RUBES, DEN HE MUZT BE EVILZ ANDZ I GOTZ TO HATEZ HIM!!!!!"
if they're jealous, and are just shy to ask you, then tell them about how to solve it... if they show no interest, ignore them. If they're amazed and don't want to show it... I normally ignore them because they obviously don't want to learn and would rather watch a cuber do it. if they don't like the noise (pretty unlikeley) just avoid them. case 5, just think of a good comeback... case 6, don't bother making a comeback... because they have to organize their brains...