What is 3/8 - 2/5?

Here's how to subtract 2/5 from 3/8:

Step 1

We can't subtract two fractions with different denominators. So you need to get a common denominator. To do this, you'll multiply the denominators times each other... but the numerators have to change, too. They get multiplied by the other term's denominator.

So we multiply 3 by 5, and get 15.

Then we multiply 2 by 8, and get 16.

Next we give both terms new denominators -- 8 × 5 = 40.

So now our fractions look like this:

Step 2

Since our denominators match, we can subtract the numerators.

15 − 16 = -1

So the answer is:

Step 3

Last of all, we need to simplify the fraction, if possible. Can it be reduced to a simpler fraction?

To find out, we try dividing it by 2...

No good. 2 is larger than -1. So we're done reducing.