Answer:
The differential equation is 
Step-by-step explanation:
Differential equation for the rate of change in radiation level:
Radiation level is R.
Rate of change indicates that the radiation level R varies in function of time t, which mathematically means that we have:

After the reactor is shut down, the radiation from the nitrogen-17 decreases in such a way that the rate of change in the radiation level is directly proportional to the radiation level.
Rate of change is k. Decreases means that k is negative. Proportional to the radiation level of R means that -k multiplies R. So the differential equation is:

I don't speak Spanish but I think that this is what you meant:
80 * 2/5 = 32
so 2/5 of 80 % is 32 % (80/5 * 2)
-5 as that you would have to count that places to the left. You end decimal would have to be between 1 and 10, so it would not count the 8. I'm sorry if my explanation is not good, but that is the right answer
Answer:
SO THE FIRST ANSWER IS 540 FEET AND THE SECOND ANSWER IS YEA U CAN