Subtract 21/7 from 21/18, Solve 1 3/18

Subtract 21/7 from 21/18

1^st number: 1 3/18, 2^nd number: 3 0/7

21/18 - 21/7 is -11/6.

Find the least common denominator or LCM of the two denominators:
LCM of 18 and 7 is 126

Next, find the equivalent fraction of both fractional numbers with denominator 126
For the 1st fraction, since 18 × 7 = 126,
21/18 = 21 × 7/18 × 7 = 147/126
Likewise, for the 2nd fraction, since 7 × 18 = 126,
21/7 = 21 × 18/7 × 18 = 378/126
Subtract the two like fractions:
147/126 - 378/126 = 147 - 378/126 = -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