Subtract 21/12 from 28/40, Solve 28/40

Subtract 21/12 from 28/40

1^st number: 28/40, 2^nd number: 1 9/12

28/40 - 21/12 is -21/20.

Find the least common denominator or LCM of the two denominators:
LCM of 40 and 12 is 120

Next, find the equivalent fraction of both fractional numbers with denominator 120
For the 1st fraction, since 40 × 3 = 120,
28/40 = 28 × 3/40 × 3 = 84/120
Likewise, for the 2nd fraction, since 12 × 10 = 120,
21/12 = 21 × 10/12 × 10 = 210/120
Subtract the two like fractions:
84/120 - 210/120 = 84 - 210/120 = -126/120
After reducing the fraction, the answer is -21/20

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