How to add and subtract fractions with the common denominator

The   addition of fractions with the same denominator is so easy to perform, just add their numerators and affix their common denominator.

Examples:
1.  1/2 + 1/2     =  2/2 or 1
2.  3/7 + 2/7     =  5/7
3.  8/15 + 5/15 = 13/15
4.  25/60 + 20/ 60 = 45/60 to reduce to simplest form give the prime factors
                                           so    45=      (3)(3)(5)    
                                                   60= (2)(2)(3) (5) 
                                           shaded yellow were eliminated,  answer is 3/4 

The subtraction of fractions with the same denominator or common denominator, just subtract the numerators and affix the common denominator

Examples
1.  5/6 - 2/6 = 3/6 or 1/2    why?   their prime factors are the following, shaded yellow removed.
                                                      3 = (1)(3)        
                                                      6 = (2)(3) 
                                                     the answer is 1/2
2. 4/5 - 2/5 = 2/5
3. 12/35- 10/35 = 2/35
4. 8/50 - 7/50 = 1/50
5. 9/17 - 4/17 = 5/17  

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