Subtract 20/18 from 18/21
1st number: 18/21, 2nd number: 1 2/18
18/21 - 20/18 is -16/63.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 21 and 18 is 126
Next, find the equivalent fraction of both fractional numbers with denominator 126 - For the 1st fraction, since 21 × 6 = 126,
18/21 = 18 × 6/21 × 6 = 108/126 - Likewise, for the 2nd fraction, since 18 × 7 = 126,
20/18 = 20 × 7/18 × 7 = 140/126 - Subtract the two like fractions:
108/126 - 140/126 = 108 - 140/126 = -32/126 - After reducing the fraction, the answer is -16/63
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 36/21-20/18 18/21-40/18 18/42-20/18 18/21-20/36 54/21-20/18 18/21-60/18 18/63-20/18 18/21-20/54 90/21-20/18 18/21-20/90