Subtract 42/72 from 5/21, Solve 5/21

Subtract 42/72 from 5/21

5/21 - 42/72 is -29/84.

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

Next, find the equivalent fraction of both fractional numbers with denominator 504
For the 1st fraction, since 21 × 24 = 504,
5/21 = 5 × 24/21 × 24 = 120/504
Likewise, for the 2nd fraction, since 72 × 7 = 504,
42/72 = 42 × 7/72 × 7 = 294/504
Subtract the two like fractions:
120/504 - 294/504 = 120 - 294/504 = -174/504
After reducing the fraction, the answer is -29/84

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