You would add 3 1/2 + 1 3/7. To do this you have to find a common denominator which would be 14. And then whatever you multiplied the denominator by to get to 14 (2 and 7) you multiply it times the top. Once you do this you should get 3 7/14 and 1 6/14 then you just simply add. Giving you 4 13/14