Answers

Subtract 70/21 from 90/20

1^st number: 4 10/20, 2^nd number: 3 7/21

90/20 - 70/21 is 7/6.

Steps for subtracting fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 20 and 21 is 420
   
   Next, find the equivalent fraction of both fractional numbers with denominator 420
2. For the 1st fraction, since 20 × 21 = 420,
   90/20 = 90 × 21/20 × 21 = 1890/420
3. Likewise, for the 2nd fraction, since 21 × 20 = 420,
   70/21 = 70 × 20/21 × 20 = 1400/420
4. Subtract the two like fractions:
   1890/420 - 1400/420 = 1890 - 1400/420 = 490/420
5. After reducing the fraction, the answer is 7/6
6. In mixed form: 11/6

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