Ok, so I'll make an example problem to show.
There's a forest in town and it's recorded that there are 5 bears and 100 squirrels in it.
First, you would make this a ratio so that would be 5:100. 5 being the bears and 100 being the squirrels.
To simplify it, just make it into a fraction. The first number, going from left to right, would be the numerator and 100 would be the denominator.
5
-----
100
To simplify, just divide by the greatest common factor which would be 5 in this case.
5 1
----- / 5 = ----
100 20
