Question 11= B
Question 13= C
I don't know how to do question 12
Answer:
The maximum cost is 41 dollars per necklace.
Step-by-step explanation:
The average cost in dollars/necklace is given by :
.....(1)
Where
x is the number of necklaces that are created
To maximize the cost, find the value of x by putting dC/dx = 0

Now put the value of x = 7 in equation (1).

Hence, the maximum cost is 41 dollars per necklace.
Here is your answer
A. 1,3,5,7,9,11,.....
REASON :
In an AP their is a common difference between two consecutive terms.
i.e. t2-t1=t3-t2=t4-t3=....= constant
The option A satisfies above condition.
HOPE IT IS USEFUL
Answer:

Step-by-step explanation:
As we can see the given expression as three complex parts and all are being multiplied.
Lets simplify each part separately and then multiply all of them in the end
Part1
Cancelling 8 in numerator with 8 in denominator



Part2

simpliying



Part3
Third part is
, and it does not need to be further simplified
Now multiplying all the three parts





So our final answer is 
-10x is the final answer
Hope this helps