Answers

Subtract 15/20 from 8/21

8/21 - 15/20 is -31/84.

Steps for subtracting fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 21 and 20 is 420
   
   Next, find the equivalent fraction of both fractional numbers with denominator 420
2. For the 1st fraction, since 21 × 20 = 420,
   8/21 = 8 × 20/21 × 20 = 160/420
3. Likewise, for the 2nd fraction, since 20 × 21 = 420,
   15/20 = 15 × 21/20 × 21 = 315/420
4. Subtract the two like fractions:
   160/420 - 315/420 = 160 - 315/420 = -155/420
5. After reducing the fraction, the answer is -31/84

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