Subtract 84/8 from 21/42, Solve 21/42

Subtract 84/8 from 21/42

1^st number: 21/42, 2^nd number: 10 4/8

21/42 - 84/8 is -10/1.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 8 is 168

Next, find the equivalent fraction of both fractional numbers with denominator 168
For the 1st fraction, since 42 × 4 = 168,
21/42 = 21 × 4/42 × 4 = 84/168
Likewise, for the 2nd fraction, since 8 × 21 = 168,
84/8 = 84 × 21/8 × 21 = 1764/168
Subtract the two like fractions:
84/168 - 1764/168 = 84 - 1764/168 = -1680/168
After reducing the fraction, the answer is -10/1

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