Answer:
5:4
Explanation:
If both are even, I usually like to divide both the numerator and the denominator by 2 until I can no longer do so (meaning, dividing either of them by 2 would result in a fraction). This is, of course, if you cannot think of the greatest common factor off the top of your head.
We cannot divide by 2 anymore, however, it is a lot simpler to detect now that we can divide by 3.