Answer
$3b$
Work Step by Step
With $27=3^3$, then
$\ln27 = \ln(3^3)$
Recall that $\log_a \left(M^r\right) = r \log_a M$.
Using the rule above gives:
$\ln(3^3) = 3 \ln3$
With $\ln3 = b$, then
$3 \ln3 = 3b$
Therefore,
$\ln27 = \boxed{3b}$
