Answer:
The half-life of the radioactive substance is of 3.25 days.
Step-by-step explanation:
The amount of radioactive substance is proportional to the number of counts per minute:
This means that the amount is given by the following differential equation:

In which k is the decay rate.
The solution is:

In which Q(0) is the initial amount:
8000 counts per minute on a Geiger counter at a certain time
This means that 
500 counts per minute 13 days later.
This means that
. We use this to find k.







So

Determine the half-life of the radioactive substance.
This is t for which Q(t) = 0.5Q(0). So







The half-life of the radioactive substance is of 3.25 days.
X=11
-5(x+1) = -3(2x-2)
distribute
-5x-5= -6x+6
both +6x
x-5=6
plus 5 on both
x=11
Answer:
La frecuencia cardíaca normal de un oso pardo cuando no está hibernando es de 50 latidos por minuto.
Step-by-step explanation:
15. 5/9, 9.5%, 0.95, 99%
16. 50%, 0.35, 38% 3/8
17. 4/5, 0.45, 54%, 44.5%
18. 20%, 0.3, 1/3, 3%
Hope this is right