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:



The total charge for Juan in the parking spot would be $2.25.
Since we know one of those 8 hours is 50 cents, we can multiply .25 by 7 which would give us 1.75. Then we know that the first hour, as stated above, is going to be .50, so we can add that to our total which is 2.25.
Hope this helps!
You would have to divide 16.50 into 3 then put your answer down hope this helps
X should equal 100. Hope this helps :)