 # What is 7/9 + 3/12? 7 9
+
 3 12

## Step 1

Can you add yet? Nope! The denominators don't match. We need a common denominator. So next we take both denominators and multiply them. Next, take each numerator and multiply it by the denominator of the other term.

So, we multiply 7 by 12, and get 84, then we multiply 9 by 12 and get 108. Now for the second term. You multiply 3 by 9, and get 27, then multiply 9 by 12 and get 108. We now have a new problem, that looks like this:

 84 108
+
 27 108

## Step 2

Since our denominators match, we can add the numerators.

84 + 27 = 111

That gives us the sum, which is

 111 108

## Step 3

Now, do we need to simplify this fraction?

First, we attempt to divide it by 2...

Nope. Try the next prime number, 3...

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

 111 108
÷ 3 =
 37 36

Now, try the same number again.

Nope. Try the next prime number, 5...

Nope. Try the next prime number, 7...

Nope. Try the next prime number, 11...

Nope. Try the next prime number, 13...

Nope. Try the next prime number, 17...

Nope. Try the next prime number, 19...

Nope. Try the next prime number, 23...

Nope. Try the next prime number, 29...

Nope. Try the next prime number, 31...

Nope. Try the next prime number, 37...

No good. 37 is larger than 36. So we're done reducing.