The formula for the area (A) of the sector is,
[tex]A=\frac{\theta}{360^0}\times\pi r^2[/tex]Given
[tex]\begin{gathered} r=18cm \\ A=234\pi cm^2 \end{gathered}[/tex]Therefore,
[tex]234\pi=\frac{\theta}{360}\times\pi(18)^2[/tex]Solve for θ
[tex]\begin{gathered} \frac{θ}{360}\pi \left(18\right)^2=234\pi \\ \frac{9\pi θ}{10}=234\pi \\ \frac{10\times \:9\pi θ}{10}=10\times \:234\pi \\ 9\pi θ=2340\pi \\ \mathrm{Divide\:both\:sides\:by\:}9\pi \\ \frac{9\pi θ}{9\pi }=\frac{2340\pi }{9\pi } \\ \thereforeθ=260^0 \end{gathered}[/tex]Hence, the answer is
[tex]260^0[/tex]