When you declare that something of type int is returned from a method, as you have in your fnum and snum methods, you must return something. As you have found it is an error if you do not return anything. For example:
You must return something of type int using the return statement.
Also, you nearly got the code tags right but I fixed them up for you this time. I encourage you to use the "Preview" feature when composing your message to see if it looks alright before submitting. It's saved me from embarrassment many a time.