Answer
$t = 32768$
Work Step by Step
$\log_8 t = 5$
$8^{5} = t$
$t = 32768$
Check:
$\log_8 t \overset{?}{=} 5$
$\log_8 (32768) \overset{?}{=} 5$
$\log_8 (8^{5}) \overset{?}{=} 5$
$5\log_8 (8) \overset{?}{=} 5$
$5(1) \overset{?}{=} 5$
$5 = 5$