Subtract 90/27 from 40/42, Solve 40/42

Subtract 90/27 from 40/42

1^st number: 40/42, 2^nd number: 3 9/27

40/42 - 90/27 is -50/21.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 27 is 378

Next, find the equivalent fraction of both fractional numbers with denominator 378
For the 1st fraction, since 42 × 9 = 378,
40/42 = 40 × 9/42 × 9 = 360/378
Likewise, for the 2nd fraction, since 27 × 14 = 378,
90/27 = 90 × 14/27 × 14 = 1260/378
Subtract the two like fractions:
360/378 - 1260/378 = 360 - 1260/378 = -900/378
After reducing the fraction, the answer is -50/21

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