This is a good question... but is there multiple choice, i want to know if my answer matches
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-12 -6a = -48
Add 12 to isolate -6a
-6a = -36
Divide by -6 on both sides to isolate a
a = 6
So, here we have an exponential function.
Remember that an exponential function has the form:

Where a represents an initial amount, and r is the rate of this amount to change. (Increase, or decrease).
So, given that the population of City A in 2000 was 40 thousand people and the population increased by 13% each year, we can say that

So,

For city B:

But something different happens with city C. This is not an exponential function, this is a linear function.
So,

Answer:
<em>97.5 sq. ft.</em>
Step-by-step explanation:
Im presuming the question asks to find area of the shaded region.
First of all, the total figure is a rectangle. We can write an expression(in words) for the shaded area.
<em>Shaded Area = Area of Rectangle - Area of Small Triangle(White) - Area of Large Triangle(White)</em>
Now, we find respective areas.
Area of rectangle:
length * width = (5+10) * (12) = 15 * 12 = 180
Area of Small Triangle (white):
A = (1/2) * base * height = (1/2) * 5 * (12-3) = (1/2) * 5 * 9 = 22.5
Area of Large Triangle (white):
A = (1/2) * base * height = (1/2) * 10 * (12) = 60
Now, we find area of shaded region:
<em>Shaded Area = Area of Rectangle - Area of Small Triangle(White) - Area of Large Triangle(White)</em>
<em>Shaded Area = 180 - 22.5 - 60 = 97.5 sq. ft.</em>
Answer: The volume(v) is 438.77.
Explanation: The formula for a right circular cone is in the image.