Subtract 21/8 from 18/21
1st number: 18/21, 2nd number: 2 5/8
18/21 - 21/8 is -99/56.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 8 is 168
Next, find the equivalent fraction of both fractional numbers with denominator 168 - For the 1st fraction, since 21 × 8 = 168,
18/21 = 18 × 8/21 × 8 = 144/168 - Likewise, for the 2nd fraction, since 8 × 21 = 168,
21/8 = 21 × 21/8 × 21 = 441/168 - Subtract the two like fractions:
144/168 - 441/168 = 144 - 441/168 = -297/168 - After reducing the fraction, the answer is -99/56
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 36/21-21/8 18/21-42/8 18/42-21/8 18/21-21/16 54/21-21/8 18/21-63/8 18/63-21/8 18/21-21/24 90/21-21/8 18/21-21/40 18/21-21/56