Subtract 18/21 from 28/42
28/42 - 18/21 is -4/21.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 21 is 42
Next, find the equivalent fraction of both fractional numbers with denominator 42 - For the 1st fraction, since 42 × 1 = 42,
28/42 = 28 × 1/42 × 1 = 28/42 - Likewise, for the 2nd fraction, since 21 × 2 = 42,
18/21 = 18 × 2/21 × 2 = 36/42 - Subtract the two like fractions:
28/42 - 36/42 = 28 - 36/42 = -8/42 - After reducing the fraction, the answer is -4/21
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 56/42-18/21 28/42-36/21 28/84-18/21 28/42-18/42 84/42-18/21 28/42-54/21 28/42-18/63 28/42-90/21