Subtract 42/56 from 15/21, Solve 15/21

Subtract 42/56 from 15/21

15/21 - 42/56 is -1/28.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 56 is 168

Next, find the equivalent fraction of both fractional numbers with denominator 168
For the 1st fraction, since 21 × 8 = 168,
15/21 = 15 × 8/21 × 8 = 120/168
Likewise, for the 2nd fraction, since 56 × 3 = 168,
42/56 = 42 × 3/56 × 3 = 126/168
Subtract the two like fractions:
120/168 - 126/168 = 120 - 126/168 = -6/168
After reducing the fraction, the answer is -1/28

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