/sci/ - Science & Math

So I was sitting in class today, bored, and I thought of a math problem. I'm not sure if it's been thought of before (though it probably has) and I was wondering if anyone has any info on it.

In my head, it started off as A and B are any numbers, say long, weird decimals, and M and N are integers. I was wondering if, for any A and B values, there exists an M and N where MA = NB. This evolved in my head to M/N=B/A, and so (I think) the final question is: Can every number be expressed as a ratio of 2 integers?

Sorry if this is stupid or obvious, or if I'm missing something