Did you mean to have (4,7) as an element of F and (5,2) 
as an element of G?  That would mean that 
F has domain {1,3,4} whereas G has domain {1,3,5}.

If you didn't make a typo, we can only use the common 
domain {1,3}, and ignore the ordered pairs (4,7) in F
and (5,2) in G, since they do not have the same first
coordinate.

F+G = {(1,2+4), (3,5+0)}

or upon simplifying:

F+G = {(1,6), (3,5)}

---------------------

G/F = {(1,4/2), (3,0/5)} 

or, upon simplifying:
 
G/F = {(1,2),(3,0)}

Edwin