Answer:
[tex]\large\boxed{x=\dfrac{6b}{\pi n^2}}[/tex]
Step-by-step explanation:
[tex]b=\dfrac{1}{6}\pi n^2x\qquad\text{multiply both sides by 6}\\\\6b=\pi n^2x\qquad\text{divide both sides by}\ \pi n^2\neq0\\\\\dfrac{6b}{\pi n^2}=b[/tex]
