Subtract 80/72 from 21/28, Solve 21/28

Subtract 80/72 from 21/28

1^st number: 21/28, 2^nd number: 1 8/72

21/28 - 80/72 is -13/36.

Find the least common denominator or LCM of the two denominators:
LCM of 28 and 72 is 504

Next, find the equivalent fraction of both fractional numbers with denominator 504
For the 1st fraction, since 28 × 18 = 504,
21/28 = 21 × 18/28 × 18 = 378/504
Likewise, for the 2nd fraction, since 72 × 7 = 504,
80/72 = 80 × 7/72 × 7 = 560/504
Subtract the two like fractions:
378/504 - 560/504 = 378 - 560/504 = -182/504
After reducing the fraction, the answer is -13/36

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