Subtract 18/7 from 42/21
1st number: 2 0/21, 2nd number: 2 4/7
42/21 - 18/7 is -4/7.
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,
42/21 = 42 × 1/21 × 1 = 42/21 - Likewise, for the 2nd fraction, since 7 × 3 = 21,
18/7 = 18 × 3/7 × 3 = 54/21 - Subtract the two like fractions:
42/21 - 54/21 = 42 - 54/21 = -12/21 - After reducing the fraction, the answer is -4/7
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 84/21-18/7 42/21-36/7 42/21-18/14 42/21-54/7 42/63-18/7 42/21-18/21 42/21-90/7 42/21-18/35 42/21-18/49