Answer:

Step-by-step explanation:
The time constant of the isotope is:


The decay of the isotope is described by the following model:

Now, the time is cleared in the equation:



Answer:
B
Step-by-step explanation:
2x-5y=13.........(1) × 3
-3x+2y=13.......(2) × 2
6x - 15y = 39
-6x + 4y = 26
Adding
6x - 6x - 15y + 4y = 13 + 13
Answer:
5*2+1/2*-2
11/2*-2
-11
Step-by-step explanation: