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:
[tex] \frac{\frac{21}{3}}{\frac{36}{3}} = \frac{7}{12} [/tex]
Therefore, the simplified form is given by:
[tex] \frac{7}{12} [/tex]
Answer:
[tex] \frac{21}{36} [/tex] in simplest form is:
[tex] \frac{7}{12} [/tex]