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Subtract 20/21 from 15/28

15/28 - 20/21 is -5/12.

Steps for subtracting fractions

  1. Find the least common denominator or LCM of the two denominators:
    LCM of 28 and 21 is 84
  2. For the 1st fraction, since 28 × 3 = 84,
    15/28 = 15 × 3/28 × 3 = 45/84
  3. Likewise, for the 2nd fraction, since 21 × 4 = 84,
    20/21 = 20 × 4/21 × 4 = 80/84
  4. Subtract the two fractions:
    45/84 - 80/84 = 45 - 80/84 = -35/84
  5. After reducing the fraction, the answer is -5/12

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