running out of time!! help fast!

okay, some quick help..

i understand mostly everything, except, using similarity postulates. how do i know which one is what? can anyone show an example in a triangle to show when a triangle is AA (angle angle) or SAS (side angle side) ect..

how about, proving that 2 triangles are in proportion.. i dont understand the defenition of proportion or how to prove it.

one last thing i need help on, angles of a polygon.. how do you know when the figure is a polygon? or convex or non convex polygon..

hopefully if i get an A in the final, i will have the highest grade in the class.. please, if anyone can help me fast!!

thank you!!

-mattballer082