Well, both 4 and 56 can be divided by two, which simplifies the number to 2/28. Both 2 and 28 can be divided by two, which simplifies to 1/14. Therefore 1/14 is the simplest form.
You could also do this faster by discovering that both 4 and 56 can be divided by four, and then simplify in one step.
Basically, the way to simplify is to find a common number that both numbers can be divided by. Continue doing that until there is not a number that both numbers can be divided by.
Hope this helps! If you have any questions I will do my best to answer in the comments.
