Subtract 42/27 from 20/21, Solve 20/21

Subtract 42/27 from 20/21

1^st number: 20/21, 2^nd number: 1 15/27

20/21 - 42/27 is -38/63.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 27 is 189

Next, find the equivalent fraction of both fractional numbers with denominator 189
For the 1st fraction, since 21 × 9 = 189,
20/21 = 20 × 9/21 × 9 = 180/189
Likewise, for the 2nd fraction, since 27 × 7 = 189,
42/27 = 42 × 7/27 × 7 = 294/189
Subtract the two like fractions:
180/189 - 294/189 = 180 - 294/189 = -114/189
After reducing the fraction, the answer is -38/63

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