We can set up this question like this to help understand it better....
Bananas : Apples
6 : 4 -----> *** You would think this is the answer but it isn't! ***
Why you may ask... it's because this ratio can be simplified. Yes it is very much like a fraction!
So when we simplify 6 : 4 we will get this ratio as the answer!!
3 : 2
I hope this helps you! :D