Subtract 3/21 from 21/72, Solve 21/72

Subtract 3/21 from 21/72

21/72 - 3/21 is 25/168.

Find the least common denominator or LCM of the two denominators:
LCM of 72 and 21 is 504

Next, find the equivalent fraction of both fractional numbers with denominator 504
For the 1st fraction, since 72 × 7 = 504,
21/72 = 21 × 7/72 × 7 = 147/504
Likewise, for the 2nd fraction, since 21 × 24 = 504,
3/21 = 3 × 24/21 × 24 = 72/504
Subtract the two like fractions:
147/504 - 72/504 = 147 - 72/504 = 75/504
After reducing the fraction, the answer is 25/168

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