What is 21/63 - 4/12?

Here's how to subtract 4/12 from 21/63:

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 21 by 12, and get 252.

Then we multiply 4 by 63, and get 252.

Next we give both terms new denominators -- 63 × 12 = 756.

So now our fractions look like this:

Step 2

Since our denominators match, we can subtract the numerators.

252 − 252 = 0

So the answer is: