#8: $900. (I found this answer by multiplying 3000 and 0.3 by the way)
#9: 160 miles. I found this answer by multiplying 80 by two, since two halves/50% make a whole or 100%.
Answer:
The correct answer is:
Between 600 and 700 years (B)
Step-by-step explanation:
At a constant decay rate, the half-life of a radioactive substance is the time taken for the substance to decay to half of its original mass. The formula for radioactive exponential decay is given by:

First, let us calculate the decay constant (k)

Next, let us calculate the half-life as follows:

Therefore the half-life is between 600 and 700 years
It's be a line that crosses the y-axis at (0,7) and has a slope of -3 or -3/1.
Answer: The lenght of the missing side is 4 cm
Step-by-step explanation:
The correct question is:
<em>The perimeter of the rectangle is 20cm . One side is 6cm. What is the length of the missing side?</em>
So, to answer it we have to apply the next formula:
Perimeter of a rectangle = 2 width + 2 length
Replacing with the values given: (assuming that the side given is the length of the rectangle)
20 = 2(6) + 2x
Solving for x:
20 =12 +2x
20-12 =2x
8 =2x
8/2 =x
4=x
The length of the missing side is 4 cm
Feel free to ask for more if needed or if you did not understand something.