Subtract 70/90 from 12/21, Solve 12/21

Subtract 70/90 from 12/21

12/21 - 70/90 is -13/63.

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,
12/21 = 12 × 30/21 × 30 = 360/630
Likewise, for the 2nd fraction, since 90 × 7 = 630,
70/90 = 70 × 7/90 × 7 = 490/630
Subtract the two like fractions:
360/630 - 490/630 = 360 - 490/630 = -130/630
After reducing the fraction, the answer is -13/63

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