Subtract 21/12 from 15/42
1st number: 15/42, 2nd number: 1 9/12
15/42 - 21/12 is -39/28.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 12 is 84
Next, find the equivalent fraction of both fractional numbers with denominator 84 - For the 1st fraction, since 42 × 2 = 84,
15/42 = 15 × 2/42 × 2 = 30/84 - Likewise, for the 2nd fraction, since 12 × 7 = 84,
21/12 = 21 × 7/12 × 7 = 147/84 - Subtract the two like fractions:
30/84 - 147/84 = 30 - 147/84 = -117/84 - After reducing the fraction, the answer is -39/28
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 30/42-21/12 15/42-42/12 15/84-21/12 15/42-21/24 45/42-21/12 15/42-63/12 15/42-21/36 75/42-21/12 15/42-21/60 15/42-21/84