Answer:
The product of 12 and k is 84
According to the given problem, the equation is

- <u>k = 7</u> is the right answer.
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:

Every number will have only 3 digits. In the ones place, there are 5 choices. For every choice of digit made in the ones place, there are 8 possible choices for the hundreds place (you can choose from 1-9, omitting whatever is used in the ones place), and there are 8 possible choices for the tens place (you can choose from 0-9, omitting whatever has already been used elsewhere).
So there are

such numbers.
Two complementary angles must add to 90 degrees, and if you divide 90 into thirds (two parts for the larger angle, one for the smaller), then you get 30 degrees.
If the smaller angle is 30 degrees, then the larger is two times that, which is 60. 60 + 30 = 90, so the larger angle is equal to 60 degrees.
Answer:
Option D) is correct
That is x=2 , y=-5
Step-by-step explanation:
Given that the 
To find their determinants

=-8+48
=40
Therefore 

=-76+156
=80
Therefore 

=104-304
=-200
Therefore 
To find the values of x and y:

and 
x=2 and y=-5
Option D) is correct
That is x=2 , y=-5