X + 3y = 9
3x - 3y = -13
--------------add
4x = - 4
x = -4/4
x = -1
x + 3y = 9
-1 + 3y = 9
3y = 9 + 1
3y = 10
y = 10/3
solution (-1,10/3)
Answer:

Step-by-step explanation:
Let X be the number of units produced, and P be the cost of production.
#Given that 
Cost of production can be calculated as:

#Mean of the total cost is calculated as;

Hence, the mean cost of production is $2,000
#Variance of the total cost is calculated as;

Hence, the variancecost of production is $3,600
For this case we have the following equation:

Let 
We have:

By definition, given an equation of the form 
The quadratic formula, to find the solution can be written as:

In this case we have:

Substituting in the quadratic formula we have:
See attached image
Answer:
Option B
x2 =9
x4 =64
64-9 =55
4-2 = 2
55/2 = 27.5
average rate is 27.5, B is the answer
Cost divided by number of items equals each items cost
20/16= 1.25
$1.25