Subtract 20/21 from 7/9
7/9 - 20/21 is -11/63.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 9 and 21 is 63
Next, find the equivalent fraction of both fractional numbers with denominator 63 - For the 1st fraction, since 9 × 7 = 63,
7/9 = 7 × 7/9 × 7 = 49/63 - Likewise, for the 2nd fraction, since 21 × 3 = 63,
20/21 = 20 × 3/21 × 3 = 60/63 - Subtract the two like fractions:
49/63 - 60/63 = 49 - 60/63 = -11/63
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 14/9-20/21 7/9-40/21 7/18-20/21 7/9-20/42 21/9-20/21 7/9-60/21 7/27-20/21 7/9-20/63 35/9-20/21 7/45-20/21 49/9-20/21 7/63-20/21