Subtract 42/18 from 4/21, Solve 4/21

Subtract 42/18 from 4/21

1^st number: 4/21, 2^nd number: 2 6/18

4/21 - 42/18 is -15/7.

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,
4/21 = 4 × 6/21 × 6 = 24/126
Likewise, for the 2nd fraction, since 18 × 7 = 126,
42/18 = 42 × 7/18 × 7 = 294/126
Subtract the two like fractions:
24/126 - 294/126 = 24 - 294/126 = -270/126
After reducing the fraction, the answer is -15/7

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