Answers

Subtract 21/40 from 8/42

8/42 - 21/40 is -281/840.

Steps for subtracting fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 42 and 40 is 840
   
   Next, find the equivalent fraction of both fractional numbers with denominator 840
2. For the 1st fraction, since 42 × 20 = 840,
   8/42 = 8 × 20/42 × 20 = 160/840
3. Likewise, for the 2nd fraction, since 40 × 21 = 840,
   21/40 = 21 × 21/40 × 21 = 441/840
4. Subtract the two like fractions:
   160/840 - 441/840 = 160 - 441/840 = -281/840

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