Subtract 42/7 from 21/81, Solve 21/81

Subtract 42/7 from 21/81

1^st number: 21/81, 2^nd number: 6 0/7

21/81 - 42/7 is -155/27.

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,
42/7 = 42 × 81/7 × 81 = 3402/567
Subtract the two like fractions:
147/567 - 3402/567 = 147 - 3402/567 = -3255/567
After reducing the fraction, the answer is -155/27

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