Answer:
B. 6
Step-by-step explanation:
[tex]\text{use}\\\\a^{-n}=\dfrac{1}{a^n}\\\\==========================\\\\b^{-3}=\dfrac{1}{216}\\\\\dfrac{1}{b^3}=\dfrac{1}{216}\qquad\text{inverse both sides}\\\\b^2=216\to b=\sqrt[3]{216}\\\\b=6\ \text{because}\ 6^3=216[/tex]
