Subtract 15/20 from 20/42, Solve 20/42

Subtract 15/20 from 20/42

20/42 - 15/20 is -23/84.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 20 is 420

Next, find the equivalent fraction of both fractional numbers with denominator 420
For the 1st fraction, since 42 × 10 = 420,
20/42 = 20 × 10/42 × 10 = 200/420
Likewise, for the 2nd fraction, since 20 × 21 = 420,
15/20 = 15 × 21/20 × 21 = 315/420
Subtract the two like fractions:
200/420 - 315/420 = 200 - 315/420 = -115/420
After reducing the fraction, the answer is -23/84

MathStep (Works offline)

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