Farfelles and Gooberlings

In class we have been reading The Last of the Really Great Whangdoodles. We have been drawing pictures of Whangdoodles (some look like moose, others look like horses, but all look fanciful).

This made Mrs. Alaniz think about more whimsical creatures, such as farfelles and gooberlings (two creatures she came across while reading a book--which Mrs. Alaniz does quite often).

Here's a little problem to solve involving these creatures:

There were 39 creatures in Sam's drawing.  He drew 2-legged Gooberlings and 4-legged Farfelles.  If there were a total of 122 legs in the drawing, how many Gooberlings and Farfelles were in Sam's picture?

Do you know the answer:
(Hint:  Make a table or a chart to find the solution.)

(Source:  Scholastic: Tic Tac Math: Grades 5 & Up)