Subtract 18/7 from 18/21
1st number: 18/21, 2nd number: 2 4/7
18/21 - 18/7 is -12/7.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 7 is 21
Next, find the equivalent fraction of both fractional numbers with denominator 21 - For the 1st fraction, since 21 × 1 = 21,
18/21 = 18 × 1/21 × 1 = 18/21 - Likewise, for the 2nd fraction, since 7 × 3 = 21,
18/7 = 18 × 3/7 × 3 = 54/21 - Subtract the two like fractions:
18/21 - 54/21 = 18 - 54/21 = -36/21 - After reducing the fraction, the answer is -12/7
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 36/21-18/7 18/21-36/7 18/42-18/7 18/21-18/14 54/21-18/7 18/21-54/7 18/63-18/7 18/21-18/21 90/21-18/7 18/21-90/7 18/21-18/35 18/21-18/49