What is 21/63 + 7/9?

This is how you add

Step 1

Our denominators (bottom numbers) don't match, so we can't add yet.

Since 9 is evenly divided by 63, we can multiply just one term to get a common denominator.

Multiply 7 by 7, and get 49, then we multiply 9 by 7 and get 63.

So now our fractions look like this:

Step 2

Since our denominators match, we can add the numerators.

21 + 49 = 70

Now we have an answer.

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...

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

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

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

Are both the numerator and the denominator evenly divisible by 7? Yes! So we reduce it:

Now, try the same number again.

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

No good. 11 is larger than 10. So we're done reducing.

Congratulations! Here's your final answer to 21/63 + 7/9