There are 26 tiles in a bag. of these, 15 are purple, and the rest are yellow. what are the odds in favor of drawing a yellow tile?

Try drawing yourself a chart to help you figure it out.  Here is an example:

45

-

15

__

30

This leaves 30 yellow, and 15 purple.  Each letter will be used as five tiles of the color.  

(P,P,P) : (Y,Y,Y,Y,Y,Y)  

This shows the number of tiles, NOT the answer.  Because this is in the favor of the Yellow tiles, and 30 is twice the amount of 15, you will have 30:15.  To simplify this to it's SPF (smallest possible form), you would divide 30/15, which gives you 2:1.  I hope this helps you.  

there will be 35 boys in each team. : )