Basically, you divide 3 1/4 by 1/4. To do that, you have to change the mixed number into an improper fraction. 3 1/4 as an improper fraction is 13/4. I was able to find that since you simply just multiply the denominator by the whole number, 4 x 3, which is 12, then add 12 to the numerator, 1, which is 13. Finally, the improper fraction is 13/4 (the denominator stays the same). Now, we can divide the fractions. One rule about fractions: dividing them is the same as multiplying them with the reciprocal of the other. Like say for example, the reciprocal of 1/5 is 5/1.
Let's solve:
13/4 divided by 1/4 = 13/4 x 4/1 = At this point, you just multiply them straight across. 52/4 = It's not simplified since both can still be divided. So, you simplify by finding the greatest common multiple of 52 and 4, which is 4. 52 divided by 4 = 13; 4 divided by 4 = 1. 52/4 = 13/1 = 13 (any numerator with the denominator of one is a whole number when simplified)
So if Julie needs 3 1/4 cups of oatmeal, she will use 13 of 1/4 cups of oatmeal. Answer's 13. :) I really hope I helped!