SUBTRACTING FRACTIONS-68A

To SUBTRACT two fractions having the same denominator, add the numerators 
and use the common denominator. For example:

  3/4   -  2/4   =  1/4  or    3      2      1     = numerator
                              --- -  --- =  ---
                               4      4      4     = denominator
When the fractions have different denominators, you must change
to equivalent fractions with common denominators.  For example:

Step 1. Find the least  Step 2. Change to        Step 3. Add
common denominator.     equivalent fractions.  
 2     1                  12      3            12    3      9     3     1
--- - --- =  --- - ---   ---- - ----          --- - --- = --- or --- = ---
 3     6     18    18     18     18            18    18    18     6     2

NOTE; To get the common denominator  multiply the two denominators.

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