Subtract 21/18 from 15/70, Solve 15/70

Subtract 21/18 from 15/70

1^st number: 15/70, 2^nd number: 1 3/18

15/70 - 21/18 is -20/21.

Find the least common denominator or LCM of the two denominators:
LCM of 70 and 18 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 70 × 9 = 630,
15/70 = 15 × 9/70 × 9 = 135/630
Likewise, for the 2nd fraction, since 18 × 35 = 630,
21/18 = 21 × 35/18 × 35 = 735/630
Subtract the two like fractions:
135/630 - 735/630 = 135 - 735/630 = -600/630
After reducing the fraction, the answer is -20/21

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