Answer
$t=75^{\circ}$
Work Step by Step
Since May represents $x=4$, we substitute $x=4$ in the equation,
$t=60−30\cos(\frac{\pi}{6}x)$
$t=60−30\cos(\frac{\pi}{6}\times4)$
$t=60−30\cos(\frac{2\pi}{3})$
$t=60−30(-\frac{1}{2})$
$t=60-15(-1)$
$t=60+15$
$t=75^{\circ}$