Subtract 12/20 from 72/21, Solve 3 9/21

Subtract 12/20 from 72/21

1^st number: 3 9/21, 2^nd number: 12/20

72/21 - 12/20 is 99/35.

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,
12/20 = 12 × 21/20 × 21 = 252/420
Subtract the two like fractions:
1440/420 - 252/420 = 1440 - 252/420 = 1188/420
After reducing the fraction, the answer is 99/35
In mixed form: 229/35

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