Subtract 81/70 from 18/28, Solve 18/28

Subtract 81/70 from 18/28

1^st number: 18/28, 2^nd number: 1 11/70

18/28 - 81/70 is -18/35.

Find the least common denominator or LCM of the two denominators:
LCM of 28 and 70 is 140

Next, find the equivalent fraction of both fractional numbers with denominator 140
For the 1st fraction, since 28 × 5 = 140,
18/28 = 18 × 5/28 × 5 = 90/140
Likewise, for the 2nd fraction, since 70 × 2 = 140,
81/70 = 81 × 2/70 × 2 = 162/140
Subtract the two like fractions:
90/140 - 162/140 = 90 - 162/140 = -72/140
After reducing the fraction, the answer is -18/35

MathStep (Works offline)

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