Answer
$$t=\frac{1}{4}\ln3$$
Work Step by Step
$6e^{-4t}=2$
Dividing both sides by 6:
$e^{-4t}=\frac{2}{6}=\frac{1}{3}$
Taking the natural log of both sides:
$-4t=\ln{\frac{1}{3}}=\ln({3^{-1})}=-\ln3$
Solving for $t$:
$t=\frac{1}{4}\ln3$