Answers

Subtract 21/40 from 28/84

28/84 - 21/40 is -23/120.

Steps for subtracting fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 84 and 40 is 840
   
   Next, find the equivalent fraction of both fractional numbers with denominator 840
2. For the 1st fraction, since 84 × 10 = 840,
   28/84 = 28 × 10/84 × 10 = 280/840
3. Likewise, for the 2nd fraction, since 40 × 21 = 840,
   21/40 = 21 × 21/40 × 21 = 441/840
4. Subtract the two like fractions:
   280/840 - 441/840 = 280 - 441/840 = -161/840
5. After reducing the fraction, the answer is -23/120

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