For this case what we should do is rewrite the fraction in a simplified way.
To do this, we divide the numerator and the denominator by the same factor.
We have then:
\(\frac{\frac{21}{3}}{\frac{36}{3}} = \frac{7}{12}\)
Therefore, the simplified form is given by:
\(\frac{7}{12}\)
Answer:
\(\frac{21}{36}\) in simplest form is:
\(\frac{7}{12}\)