Subtract 8/5 from 21/84, Solve 21/84

Subtract 8/5 from 21/84

1^st number: 21/84, 2^nd number: 1 3/5

21/84 - 8/5 is -27/20.

Find the least common denominator or LCM of the two denominators:
LCM of 84 and 5 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 84 × 5 = 420,
21/84 = 21 × 5/84 × 5 = 105/420
Likewise, for the 2nd fraction, since 5 × 84 = 420,
8/5 = 8 × 84/5 × 84 = 672/420
Subtract the two like fractions:
105/420 - 672/420 = 105 - 672/420 = -567/420
After reducing the fraction, the answer is -27/20

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