How do you write a mixed number as an improper fraction?

You divide the numerator by the denominator and leave the remainder over the original denominator.

Example:

18/12

18 divided by 12 = 1 with a remainder of 6 so,

1 and 6/12

You can reduce the fraction either before or after if you want. This would make it:

18/12=3/2

3 divided by 2 = 1 with a remainder of 1 so,

1 and 1/2 (which is the same as 1 and 6/12 when it is reduced.)