Let's add


Step 1We still have different denominators (bottom numbers), though, so we need to get a common denominator. This will make the bottom numbers match. Multiply the denominators together first. Now, multiply each numerator by the other term's denominator. Now we multiply 4 by 12, and get 48, then we multiply 9 by 12 and get 108. Now for the second term. You multiply 4 by 9, and get 36, then multiply 9 by 12 and get 108. This gives us a new problem that looks like so:


Step 2Since our denominators match, we can add the numerators. 48 + 36 = 84 So what's the answer so far?


Step 3Can this fraction be reduced? First, we attempt to divide it by 2... Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:
So far so good... let's try to divide by that number again. Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:
So far so good... let's try to divide by that number again. No good. So next you try the next prime number, which is 3... Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:
So far so good... let's try to divide by that number again. No good. So next you try the next prime number, which is 5... No good. So next you try the next prime number, which is 7... No good. So next you try the next prime number, which is 11... No good. 11 is larger than 7. So we're done reducing. And we're done! Here's the final answer to 4/9 + 4/12
