Subtract 20/18 from 12/42, Solve 12/42

Subtract 20/18 from 12/42

1^st number: 12/42, 2^nd number: 1 2/18

12/42 - 20/18 is -52/63.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 18 is 126

Next, find the equivalent fraction of both fractional numbers with denominator 126
For the 1st fraction, since 42 × 3 = 126,
12/42 = 12 × 3/42 × 3 = 36/126
Likewise, for the 2nd fraction, since 18 × 7 = 126,
20/18 = 20 × 7/18 × 7 = 140/126
Subtract the two like fractions:
36/126 - 140/126 = 36 - 140/126 = -104/126
After reducing the fraction, the answer is -52/63

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