Answers

Subtract 20/72 from 81/42

1^st number: 1 39/42, 2^nd number: 20/72

81/42 - 20/72 is 104/63.

Steps for subtracting fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 42 and 72 is 504
   
   Next, find the equivalent fraction of both fractional numbers with denominator 504
2. For the 1st fraction, since 42 × 12 = 504,
   81/42 = 81 × 12/42 × 12 = 972/504
3. Likewise, for the 2nd fraction, since 72 × 7 = 504,
   20/72 = 20 × 7/72 × 7 = 140/504
4. Subtract the two like fractions:
   972/504 - 140/504 = 972 - 140/504 = 832/504
5. After reducing the fraction, the answer is 104/63
6. In mixed form: 141/63

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