why I am not a mathematician

I was just reading something that said, basically, "X is one and a half times more likely to happen than Y". I have a hard time figuring out what that means. I would understand if it said "X is likely to happen N% more than Y".

So if Y happens 10 times, X happens 15 times, and X+Y = 25. Therefore X happens 60% of the time. Is that right?