Subtract 54/21 from 81/80, Solve 1 1/80

Subtract 54/21 from 81/80

1^st number: 1 1/80, 2^nd number: 2 12/21

81/80 - 54/21 is -873/560.

Find the least common denominator or LCM of the two denominators:
LCM of 80 and 21 is 1680

Next, find the equivalent fraction of both fractional numbers with denominator 1680
For the 1st fraction, since 80 × 21 = 1680,
81/80 = 81 × 21/80 × 21 = 1701/1680
Likewise, for the 2nd fraction, since 21 × 80 = 1680,
54/21 = 54 × 80/21 × 80 = 4320/1680
Subtract the two like fractions:
1701/1680 - 4320/1680 = 1701 - 4320/1680 = -2619/1680
After reducing the fraction, the answer is -873/560

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