You started correctly . . .The antibiotic clarithromycin is eliminated from the body according to the formula:
is amount remaining in mg remaining in body after (t) hours.
How much time will pass before the amount of drug in the body is reduced to 100 mg?
We have: .
Divide by 100: .
Take logs: .
And we have: .
Since , we have: .
. . Therefore: . hours.