What is the sum or difference of 5/7 - 1/3

ANSWER: 8/21

Step:
1. Find the GCF (Greatest Common Factor)
           The two denominator which is the bottom number have to be the same ALWAYS when adding and subtracting the fraction. So to find the GCF, you keep multiplying until you see the same number, only use the bottom number to find the GCF
      7: 7, 14, 21, 28
      3: 3, 6, 9, 12, 15, 18, 21, 24, 27
         GCF= 21

2.  5/7 -1/3
    Multiple both to get 21
        5/7 x 3/3 = 15/21
        1/3 x 7/7 = 7/21

3. Sove
     15/21 - 7/21
        = 8/21