Subtract 84/90 from 4/21, Solve 4/21

Subtract 84/90 from 4/21

4/21 - 84/90 is -26/35.

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

Next, find the equivalent fraction of both fractional numbers with denominator 630
For the 1st fraction, since 21 × 30 = 630,
4/21 = 4 × 30/21 × 30 = 120/630
Likewise, for the 2nd fraction, since 90 × 7 = 630,
84/90 = 84 × 7/90 × 7 = 588/630
Subtract the two like fractions:
120/630 - 588/630 = 120 - 588/630 = -468/630
After reducing the fraction, the answer is -26/35

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