Subtract 21/10 from 28/21, Solve 1 7/21

Subtract 21/10 from 28/21

1^st number: 1 7/21, 2^nd number: 2 1/10

28/21 - 21/10 is -23/30.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 10 is 210

Next, find the equivalent fraction of both fractional numbers with denominator 210
For the 1st fraction, since 21 × 10 = 210,
28/21 = 28 × 10/21 × 10 = 280/210
Likewise, for the 2nd fraction, since 10 × 21 = 210,
21/10 = 21 × 21/10 × 21 = 441/210
Subtract the two like fractions:
280/210 - 441/210 = 280 - 441/210 = -161/210
After reducing the fraction, the answer is -23/30

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