1 1/4 divided into three parts you mean? You can simply take 1 1/4 or 1.25 and divide that by 3.
By fraction, you would want to convert the mixed number into an improper fraction, that way, it's easier. 1 1/4 to an improper fraction is 5/4.
5/4 divided by 3
Now whenever you're dividing fractions, remember this tip: keep, change, flip. Keep the first fraction, change the division sign to a multiplication sign, and flip the second fraction.
So 3, or 3/1 is now 1/3 and the sign is now multiplication.
5/4 x 1/3 = 5/12
That's your answer!
Hope this helped!