Subtract 9/7 from 21/90, Solve 21/90

Subtract 9/7 from 21/90

1^st number: 21/90, 2^nd number: 1 2/7

21/90 - 9/7 is -221/210.

Find the least common denominator or LCM of the two denominators:
LCM of 90 and 7 is 630

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 90 × 7 = 630,
21/90 = 21 × 7/90 × 7 = 147/630
Likewise, for the 2nd fraction, since 7 × 90 = 630,
9/7 = 9 × 90/7 × 90 = 810/630
Subtract the two like fractions:
147/630 - 810/630 = 147 - 810/630 = -663/630
After reducing the fraction, the answer is -221/210

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