You can do it shorter after you learn, but this 
is the best way to learn how.  Break everything
down into prime factors, so there are no exponents. 

13*y*y*y*y*y*y*y*y + 2*13*y*y*y*y - 3*13*y*y

Now I'll do some coloring:

13*y*y*y*y*y*y*y*y + 2*13*y*y*y*y - 3*13*y*y

All three of those terms contain 13*y*y.  So that's what
you can take out of each one, and what's left goes in the
parentheses:

So you put the common red part out front, and put the blue part
inside a set of parentheses:

13*y*y(y*y*y*y*y*y + 2*y*y - 3)

Then you simplify it by bringing the exponents back in:

13y2(y6 + 2y2 - 3)

Edwin