Subtract 7/40 from 3/21, Solve 3/21

Subtract 7/40 from 3/21

3/21 - 7/40 is -9/280.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 40 is 840

Next, find the equivalent fraction of both fractional numbers with denominator 840
For the 1st fraction, since 21 × 40 = 840,
3/21 = 3 × 40/21 × 40 = 120/840
Likewise, for the 2nd fraction, since 40 × 21 = 840,
7/40 = 7 × 21/40 × 21 = 147/840
Subtract the two like fractions:
120/840 - 147/840 = 120 - 147/840 = -27/840
After reducing the fraction, the answer is -9/280

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