Answer:
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Answer:
a)
, b)
, c)
, d) 
Step-by-step explanation:
a) Let assume an initial mass m decaying at a constant rate k throughout time, the differential equation is:

b) The general solution is found after separating variables and integrating each sides:

Where
is the time constant and 
c) The time constant is:


The particular solution of the differential equation is:

d) The amount of radium after 300 years is:

Step-by-step explanation:
Given,
x = y - 3
Also,
6(y - 3) = 3y + 6
6y - 18 = 3y + 6
6y - 3y = 6 + 18
3y = 24
y = 24/3
y = 8
x = 8 - 3
x = 5
Therefore, the first number is 5 and the second number is 8.
Well first we need to make our fractions have a common denominator. Since 24 is the higher one we will turn 6 into 24. In order to do that we have to multiply our top number and bottom number by 4. 4x6=24 and 3x4=12 therefore our new fraction is 12/24. Now add 6 and 3 which is 9. After adding 6 and 3 we add our fractions. Adding fractions is kind of odd because you only add the top numbers. So, we add 10 and 12 to get 22. Our final step is figuring out if we can simplify the fraction which in this care we can! So, in order to simplify this fraction we divide by 2 which will then make our fraction 11/12 which can not be simplified. So your final answer would be 9 and 11/12. Hope this helps! :)