Here's how to subtract 3/9 from 4/12:
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 4 by 9, and get 36.
Then we multiply 3 by 12, and get 36.
Next we give both terms new denominators -- 12 × 9 = 108.
So now our fractions look like this:
Since our denominators match, we can subtract the numerators.
36 − 36 = 0
So the answer is:
|Zero divided by anything is just zero. So that's the final answer:|