Subtract 9/7 from 21/81, Solve 21/81

Subtract 9/7 from 21/81

1^st number: 21/81, 2^nd number: 1 2/7

21/81 - 9/7 is -194/189.

Find the least common denominator or LCM of the two denominators:
LCM of 81 and 7 is 567

Next, find the equivalent fraction of both fractional numbers with denominator 567
For the 1st fraction, since 81 × 7 = 567,
21/81 = 21 × 7/81 × 7 = 147/567
Likewise, for the 2nd fraction, since 7 × 81 = 567,
9/7 = 9 × 81/7 × 81 = 729/567
Subtract the two like fractions:
147/567 - 729/567 = 147 - 729/567 = -582/567
After reducing the fraction, the answer is -194/189

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