Subtract 9/12 from 21/42
21/42 - 9/12 is -1/4.
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,
21/42 = 21 × 2/42 × 2 = 42/84 - Likewise, for the 2nd fraction, since 12 × 7 = 84,
9/12 = 9 × 7/12 × 7 = 63/84 - Subtract the two like fractions:
42/84 - 63/84 = 42 - 63/84 = -21/84 - After reducing the fraction, the answer is -1/4
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42-18/12 21/84-9/12 21/42-9/24 63/42-9/12 21/42-27/12 21/42-9/36 21/42-45/12 21/42-9/60 21/42-63/12 21/42-9/84