Subtract 90/80 from 5/21, Solve 5/21

Subtract 90/80 from 5/21

1^st number: 5/21, 2^nd number: 1 10/80

5/21 - 90/80 is -149/168.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 80 is 1680

Next, find the equivalent fraction of both fractional numbers with denominator 1680
For the 1st fraction, since 21 × 80 = 1680,
5/21 = 5 × 80/21 × 80 = 400/1680
Likewise, for the 2nd fraction, since 80 × 21 = 1680,
90/80 = 90 × 21/80 × 21 = 1890/1680
Subtract the two like fractions:
400/1680 - 1890/1680 = 400 - 1890/1680 = -1490/1680
After reducing the fraction, the answer is -149/168

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