Subtract 90/72 from 1/21, Solve 1/21

Subtract 90/72 from 1/21

1^st number: 1/21, 2^nd number: 1 18/72

1/21 - 90/72 is -101/84.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 72 is 504

Next, find the equivalent fraction of both fractional numbers with denominator 504
For the 1st fraction, since 21 × 24 = 504,
1/21 = 1 × 24/21 × 24 = 24/504
Likewise, for the 2nd fraction, since 72 × 7 = 504,
90/72 = 90 × 7/72 × 7 = 630/504
Subtract the two like fractions:
24/504 - 630/504 = 24 - 630/504 = -606/504
After reducing the fraction, the answer is -101/84

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