Question

Can someone help me to understand how the answer is 11? In particular, I'm confused by the return statement on line 6. http://imgur.com/ly59hAQ

Answer 1

That looks like a Fibinocci sequence. Try stepping through it with the values 2, 1 and see what's going on.

Answer 2

The return statement on line six is part of the recursive algorithm given to us. That's what we need to work with.
For example,

that's the meaning of line six.
Lines 2 and 3 say that if one of the values become zero, it will return 1.
So if we draw a tree diagram, the branches end when one of the numbers become zero.
The value returned will be the number of leaves (extremity of branches).