There are two acceptable ways of solving this. I'll show both (just in case one of them doesn't align with the information from your textbook).
Option 1 (fast and easy):The following is the equation for the area of a regular pentagon with side length s.

Plug s=12 into the equation.


The third choice should be your answer.
Option 2 (much more complicated):The area of a regular polygon can be solved with the following formula.

Let's solve for the apothem.
A pentagon can be divided into 5 congruent isosceles triangles. The vertex angle will be 360/5, or 72 degrees.
An isosceles triangle can be divided into two right triangles. One of the angles of the right triangle will be 72/2, or 36 degrees.
The leg opposite of the 36 degree angle will be 12/2, or 6 inches long.


The apothem is about 8.26 inches.
The perimeter is 12*5, or 60 inches.



(it seems that we're off by 0.1 due to rounding errors)
The answer is the third choice. Hope this helps! :)
A. How many kilowatt hours of electricity did the Smiths use during February?
Kilowatt hours of electricity the Smiths used during February:
Meter read on March 1 - meter read on February 1 =
20,288 kilowatt hours - 19,423 kilowatt hours =
865 kilowatt hours
Answer: The Smiths used 865 kilowatt hours of electricity during February
b. How many kilowatt hours did they use during March?
Kilowatt hours of electricity the Smiths used during March:
Meter read on April 1 - meter read on March 1 =
21,163 kilowatt hours - 20,288 kilowatt hours =
875 kilowatt hours
Answer: The Smiths used 875 kilowatt hours of electricity during March
Answer:

Step-by-step explanation:

Answer:
8a^3.
Step-by-step explanation:
(a+b)^3=a^3+b^3+3a^2b+3ab^2
(a-b)^3=a^3-b^3-3a^2b+3ab^2
(a+b)^3+(a-b)^3=2a^3+6ab^2
According to the question
(a+b)^3+(a-b)^3+6a(a^2-b^2)
Put in the value
=2a^3+6ab^2 +6a^3–6ab^2
=8a^3