My other answer was was lacking (I also believe I should have furthermore edited it.), therefore I will attempt to explain the steps correctly this time. I don't know what exactly is requested nor what you are learning, but I suspect it would be combinations, factorials, and/or permutations, something along those lines. Firstly I figured out my answer using factorials.
FROM: F,R,O,M. This obtains 4 letters.
4! (1 x 2 x 3 x 4)= 24
I am unsure if this is what you are looking for though. I hope this helped a bit.
