Answer
$t=60^{\circ}$
Work Step by Step
Since October represents $x=9$, we substitute $x=9$ in the equation,
$t=60−30\cos(\frac{\pi}{6}x)$
$t=60−30\cos(\frac{\pi}{6}\times9)$
$t=60−30\cos(\frac{9\pi}{6})$
$t=60−30(0)$
$t=60-0$
$t=60^{\circ}$