Similar triangles desperate help

[f1f2f3]

I have a few similar triangles problems. I'm really not sure how to do them. Could you please help me, or at least get me started on how to solve it.
Thank you very much!

 

[Denis]

This is not a classroom...go read up on similar triangles:
http://www.google.ca/search?hl=en&sourc ... =&aq=f&oq=

Then try and solve; come back showing how far you got.