Subtract 63/42 from 81/80, Solve 1 1/80

Subtract 63/42 from 81/80

1^st number: 1 1/80, 2^nd number: 1 21/42

81/80 - 63/42 is -39/80.

Find the least common denominator or LCM of the two denominators:
LCM of 80 and 42 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 42 × 40 = 1680,
63/42 = 63 × 40/42 × 40 = 2520/1680
Subtract the two like fractions:
1701/1680 - 2520/1680 = 1701 - 2520/1680 = -819/1680
After reducing the fraction, the answer is -39/80

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