Subtract 80/21 from 40/72, Solve 40/72

Subtract 80/21 from 40/72

1^st number: 40/72, 2^nd number: 3 17/21

40/72 - 80/21 is -205/63.

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,
40/72 = 40 × 7/72 × 7 = 280/504
Likewise, for the 2nd fraction, since 21 × 24 = 504,
80/21 = 80 × 24/21 × 24 = 1920/504
Subtract the two like fractions:
280/504 - 1920/504 = 280 - 1920/504 = -1640/504
After reducing the fraction, the answer is -205/63

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