That would be 1/4 because in order to do simplest form for this you need to know what times 3 would get to 14. 3x1=3 so now I have to find out what do you have to multiply to get to 12 by multiplying by 3. Oh! I found it: It's 3x4=12 so, 1 is the numerator and 4 is the denominator. Put that together and your answer is 1/4! :D
I'm glad to help!