Subtract 70/30 from 21/28, Solve 21/28

Subtract 70/30 from 21/28

1^st number: 21/28, 2^nd number: 2 10/30

21/28 - 70/30 is -19/12.

Find the least common denominator or LCM of the two denominators:
LCM of 28 and 30 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 28 × 15 = 420,
21/28 = 21 × 15/28 × 15 = 315/420
Likewise, for the 2nd fraction, since 30 × 14 = 420,
70/30 = 70 × 14/30 × 14 = 980/420
Subtract the two like fractions:
315/420 - 980/420 = 315 - 980/420 = -665/420
After reducing the fraction, the answer is -19/12

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