Subtract 63/18 from 20/21, Solve 20/21

Subtract 63/18 from 20/21

1^st number: 20/21, 2^nd number: 3 9/18

20/21 - 63/18 is -107/42.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 18 is 126

Next, find the equivalent fraction of both fractional numbers with denominator 126
For the 1st fraction, since 21 × 6 = 126,
20/21 = 20 × 6/21 × 6 = 120/126
Likewise, for the 2nd fraction, since 18 × 7 = 126,
63/18 = 63 × 7/18 × 7 = 441/126
Subtract the two like fractions:
120/126 - 441/126 = 120 - 441/126 = -321/126
After reducing the fraction, the answer is -107/42

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