Answer:
5
Step-by-step explanation:
11-3(2)=
11-6=
5
Answer:
7 hours
Step-by-step explanation:
Since, the final amount of caffeine formula would be,

Where,
P = Initial value,
r = rate per period,
t = number of periods,
Here, r = 10% = 0.10, t = h, A = 


Taking log both sides,



Hence, after 7 hours the amount of caffeine in a body to reduce by half.