How do you write the fraction \[\dfrac{3}{{18}}\] in the simplest form ?

Hint: In order to determine the simplest form of the above, by looking into the number we got the knowledge that this is a rational number of the form $\dfrac{p}{q}$. So to simply write the numerator and denominator in the form of their factors, since the numerator is a prime number so no factors can be possible but denominator $18$ can be written as $6 \times 3$. After replacing these values you will see that the number $3$ is common in both numerator and denominator so cancel out.

Complete step by step answer:
Given a rational number \[\dfrac{3}{{18}}\], in the form of $\dfrac{p}{q}$, where q is not equal to zero.
To Convert this into its simplest form , factorise the numerator as well as denominator.
Since numerator is prime number so there is no factor, but denominator can be written as $6 \times 3$
Rewriting the fraction into their factors form as
$ = \dfrac{{3 \times 1}}{{6 \times 3}}$
Cancelling out $3$ as it is common in both numerator and denominator, we get
$
   = \dfrac{{{3} \times 1}}{{6 \times {3}}} \\
   = \dfrac{1}{6} \\
 $
Therefore, the simplest form of the rational number \[\dfrac{3}{{18}}\] is equal to $\dfrac{1}{6}$.

Note: A Rational number is a number which can be expressed in the form of $\dfrac{p}{q}$, where p and q are any integer value and q is not equal to 0. Such a number is known as a rational number. To convert a fraction into percent write the fraction into the decimal form and multiply it with the number $100$.