What would make it easier for you to find the answer, is to convert the whole number, 18, into a fraction. In this case, if you want to convert 18 into a whole number, while simultaneously keeping that same number and not changing it, you would turn 18 into [tex] \frac{18}{1} [/tex].
Then, you multiply, like how you would multiply any other fraction.
But I believe there is a way to simplify this. I believe 6 goes into both the numerator and the denominator. 6 goes into 72 exactly 12 times, and 6 goes into 6 exactly one time. And there's your answer.
[tex] \frac{72}{6} [/tex] = [tex] \frac{12}{1} [/tex], which in turn equals to 12. 12 is your final answer.