Subtract 9/21 from 27/20, Solve 1 7/20

Subtract 9/21 from 27/20

1^st number: 1 7/20, 2^nd number: 9/21

27/20 - 9/21 is 129/140.

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
For the 1st fraction, since 20 × 21 = 420,
27/20 = 27 × 21/20 × 21 = 567/420
Likewise, for the 2nd fraction, since 21 × 20 = 420,
9/21 = 9 × 20/21 × 20 = 180/420
Subtract the two like fractions:
567/420 - 180/420 = 567 - 180/420 = 387/420
After reducing the fraction, the answer is 129/140

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