1/6 of 18 ?

This can be calculated in several ways.

1. By multiplication of fractions

Remember that all whole numbers k can be written in the form k/1. We multiply the numerator (top) by numerator and denominator by denominator, and get:

$$\frac{1}{6}*\frac{18}{1}= \frac{18}{6} = 3$$

2. By division of the whole number

To multiply a number with 1/x is the same as dividing it with x. We get:

$$\frac{1}{6}*18 = \frac{18}{6}= 3$$

For completeness I might add this: If you wish to multiply a whole number with a fraction where the numerator (top) is unlike 1, you simply multiply the whole number with the numerator, and divide the product with the denominator:

$$\frac{a}{b}* k = \frac{a*k}{b}$$

Nice answer Tetration