Subtract 21/84 from 75/20, Solve 3 15/20

Subtract 21/84 from 75/20

1^st number: 3 15/20, 2^nd number: 21/84

75/20 - 21/84 is 7/2.

Find the least common denominator or LCM of the two denominators:
LCM of 20 and 84 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 20 × 21 = 420,
75/20 = 75 × 21/20 × 21 = 1575/420
Likewise, for the 2nd fraction, since 84 × 5 = 420,
21/84 = 21 × 5/84 × 5 = 105/420
Subtract the two like fractions:
1575/420 - 105/420 = 1575 - 105/420 = 1470/420
After reducing the fraction, the answer is 7/2
In mixed form: 31/2

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