To make a improper fraction (eg11/4) a mixed number (eg 2 3/4) you must see how many times the numerator (number on the top) fits into the denominator (number on the bottom). This will give you the Whole number (big number) whatever is left will be the new numerator on the fraction (keeping the denominator the same).
To make a mixed number a improper fraction multiply the whole number by the denominator. Then add this number to the numerator.