Subtract 42/21 from 3/18, Solve 3/18

Subtract 42/21 from 3/18

1^st number: 3/18, 2^nd number: 2 0/21

3/18 - 42/21 is -11/6.

Find the least common denominator or LCM of the two denominators:
LCM of 18 and 21 is 126

Next, find the equivalent fraction of both fractional numbers with denominator 126
For the 1st fraction, since 18 × 7 = 126,
3/18 = 3 × 7/18 × 7 = 21/126
Likewise, for the 2nd fraction, since 21 × 6 = 126,
42/21 = 42 × 6/21 × 6 = 252/126
Subtract the two like fractions:
21/126 - 252/126 = 21 - 252/126 = -231/126
After reducing the fraction, the answer is -11/6

MathStep (Works offline)

Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad