With some simplification,
cos⁻¹(x) - 5 cos⁻¹(x) - π/3 = 2π/3
becomes
-4 cos⁻¹(x) = π
or
cos⁻¹(x) = -π/4
However, the inverse cosine function has a range of 0 ≤ cos⁻¹(x) ≤ π, so there are no solutions to this equation.
Answer:
$400
OR 
Step-by-step explanation:
$400 stays the same, 72 cents is 72/100. Simplify and voila
See the attached picture: