The Limit? what's the limit?

Limits, I kind of get some limits but when I get to a limit that I dont understand I go crazy and feel like hitting my head to the wall.:( I knoow...
well so I think I do need help!!plzzzz
The ones that I kind of dont understand are in pg.95 #11,#13 and 14.
when the function has numbers and x's or y's I get it but when it has sin,cos,tan,etc. or e,int. I dont get it. that's the only problems that I am having problems with.

When someone explains me a problem detail by detail
I always understand it the first time. So I need help detail by detail.