 # What is 3/10 - 4/12? Here's how to subtract 4/12 from 3/10:

 3 10
 4 12

## 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 12, and get 36.

Then we multiply 4 by 10, and get 40.

Next we give both terms new denominators -- 10 × 12 = 120.

So now our fractions look like this:

 36 120
 40 120

## Step 2

Since our denominators match, we can subtract the numerators.

36 − 40 = -4

 -4 120

## 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...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

 -4 120
÷ 2 =
 -2 60

Let's try dividing by 2 again...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

 -2 60
÷ 2 =
 -1 30

Let's try dividing by 2 again...

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

There you have it! The final answer is:
 3 10
 4 12
=
 1 30