Subtract 90/21 from 18/8
1st number: 2 2/8, 2nd number: 4 6/21
18/8 - 90/21 is -57/28.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 8 and 21 is 168
Next, find the equivalent fraction of both fractional numbers with denominator 168 - For the 1st fraction, since 8 × 21 = 168,
18/8 = 18 × 21/8 × 21 = 378/168 - Likewise, for the 2nd fraction, since 21 × 8 = 168,
90/21 = 90 × 8/21 × 8 = 720/168 - Subtract the two like fractions:
378/168 - 720/168 = 378 - 720/168 = -342/168 - After reducing the fraction, the answer is -57/28
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 36/8-90/21 18/16-90/21 18/8-90/42 54/8-90/21 18/24-90/21 18/8-90/63 90/8-90/21 18/40-90/21 18/56-90/21