Subtract 80/21 from 10/90, Solve 10/90

Subtract 80/21 from 10/90

1^st number: 10/90, 2^nd number: 3 17/21

10/90 - 80/21 is -233/63.

Find the least common denominator or LCM of the two denominators:
LCM of 90 and 21 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 90 × 7 = 630,
10/90 = 10 × 7/90 × 7 = 70/630
Likewise, for the 2nd fraction, since 21 × 30 = 630,
80/21 = 80 × 30/21 × 30 = 2400/630
Subtract the two like fractions:
70/630 - 2400/630 = 70 - 2400/630 = -2330/630
After reducing the fraction, the answer is -233/63

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