Subtract 21/8 from 12/21, Solve 12/21

Subtract 21/8 from 12/21

1^st number: 12/21, 2^nd number: 2 5/8

12/21 - 21/8 is -115/56.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 8 is 168

Next, find the equivalent fraction of both fractional numbers with denominator 168
For the 1st fraction, since 21 × 8 = 168,
12/21 = 12 × 8/21 × 8 = 96/168
Likewise, for the 2nd fraction, since 8 × 21 = 168,
21/8 = 21 × 21/8 × 21 = 441/168
Subtract the two like fractions:
96/168 - 441/168 = 96 - 441/168 = -345/168
After reducing the fraction, the answer is -115/56

MathStep (Works offline)

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