please help will give brainlist!

Answer:
[tex]b=\frac{1}{6}[/tex]
Step-by-step explanation:
In [tex]f(x)=a\cos(b(x-c))+d[/tex], [tex]b[/tex] represents a constant related to the period of the function. Here's how it's related:
[tex]b=\frac{2\pi}{T}[/tex], where [tex]T[/tex] is the period of the function.
We're given [tex]T=12\pi[/tex], so solving for [tex]b[/tex]:
[tex]b=\frac{2\pi}{12\pi}=\boxed{\frac{1}{6}}[/tex]