Subtract 8/20 from 72/21, Solve 3 9/21

Subtract 8/20 from 72/21

1^st number: 3 9/21, 2^nd number: 8/20

72/21 - 8/20 is 106/35.

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
For the 1st fraction, since 21 × 20 = 420,
72/21 = 72 × 20/21 × 20 = 1440/420
Likewise, for the 2nd fraction, since 20 × 21 = 420,
8/20 = 8 × 21/20 × 21 = 168/420
Subtract the two like fractions:
1440/420 - 168/420 = 1440 - 168/420 = 1272/420
After reducing the fraction, the answer is 106/35
In mixed form: 31/35

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