Calculate  $\lim\limits_{ x\rightarrow 100 }{ \frac { 10-\sqrt { x } }{ x+5 } }$ $$\lim_{ x\rightarrow 100 }{ \frac { 10-\sqrt { x }  }{ x+5 }  } $$
Could you explain how to do this without using a calculator and using basic rules of finding limits?
Thanks

I suppose that you asked this question not because it's a difficult question, but because you don't know very well the rules to take care of over the limits.
First of all you need to know what a limit
is, what the indefinite case are, and
why they are indefinite, what's the meaning behind this word (i.e. $ \frac{\infty}{\infty})$, and how to look things when facing a limit. You need to start learning basic things, and you may also play with them by using a computer to see the graph of a function when it takes certain values near the critical values 
you are looking for. I suppose the best way for you it's to receive an elementary explanation (this is possible) but i don't know what book i may recommend you for it. 
