Answer
Approximately 9 weeks.
Work Step by Step
$$t = \frac{1}{c} \ln{\frac{A}{A-N}}$$ where $t$ is time in weeks it takes to achieve mastery of a portion of a task, $A$ is the maximum learning possible, $N$ is the portion of the learning that is to be achieved and $c$ is a constant used to measure an individual's learning style. For the question at hand, we're asked to find $t$ when $A = 12$, $N = 5$ and $c = 0.06$: $$t = \frac{1}{(0.06)} \ln \frac{(12)}{(12 - 5)}$$ $$t = \frac{\ln \frac{12}{7}}{0.06} \approx 9$$
