To find 4/7 + 1/3, I would first want to find the least common denominator. The least common denominator for theses is 21. So, To get from 7 to 21, I multiply three. What I multiply on top I must do on the bottom, so your new fraction is 12/21. For the other fraction, I multiplied 3 and 7 together to get a common denominator of 21. So the other new fraction is 7/21.
Now all you have to do is add these together. 7/21 + 12/21 = 19/21.
Thus, 4/7 + 1/3 = 19/21.
Hope this helps :)
