The equation will be of the form:

where A is the amount after t hours, and r is the decay constant.
To find the value of r, we plug the given values into the equation, giving:

Rearranging and taking natural logs of both sides, we get:


The required model is:
Log=13
t=4
So, this is because they already given you t because the four is on front of it that gives you your value. From there you will proceed to j7st do the math in your parentheses. You should get log=(1) & log=(13) because 1 times anything is that number just use the inverse of each would be eachother. So, 1x13 is the same as 13x1
The value of the digit in the tens place is 100 times as much as the value of the digit in the thousands place.
You can work this out by rearranging the equation and isolating the x.
4x + 12 = 36
4x = 36 - 12 (I moved the +12 to the other side, which means it becomes -12)
4x = 24 (36 - 12 = 24)
x = 24 / 4 (You need to isolate the x, and because it was being multiplied by 4, I divided both sides by 4 to leave me with just x)
x = 6 (24 divided by 4 is 6).