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Subtract 81/84 from 42/80

42/80 - 81/84 is -123/280.

Steps for subtracting fractions

  1. Find the least common denominator or LCM of the two denominators:
    LCM of 80 and 84 is 1680

    Next, find the equivalent fraction of both fractional numbers with denominator 1680
  2. For the 1st fraction, since 80 × 21 = 1680,
    42/80 = 42 × 21/80 × 21 = 882/1680
  3. Likewise, for the 2nd fraction, since 84 × 20 = 1680,
    81/84 = 81 × 20/84 × 20 = 1620/1680
  4. Subtract the two like fractions:
    882/1680 - 1620/1680 = 882 - 1620/1680 = -738/1680
  5. After reducing the fraction, the answer is -123/280

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