Reduce $\frac{- 36}{- 216}$ to standard form.

$\frac{- 36}{- 216}=\frac{36}{216}$ (here both the negative symbols of the numerator and denominator get cancelled).

By dividing the numerator and denominator by their highest common factor (HCF), a fraction is reduced to the standard form. 

The HCF of 36 and 216 is 36. So, divide the numerator and denominator by 36.

$\frac{36}{216}= \frac{36 ÷ 36}{216 ÷ 36}=\frac{1}{6}$

Therefore, the standard form of $\frac{- 36}{- 216}$ is $\frac{1}{6}$.