The answer would be a mathematical phrase. Hope that helped.
        
             
        
        
        
Answer:9400 backpacks
 Step-by-step explanation
Step-by-step explanation
since the number of packs to be sold in a  is represented by x,
selling price for 1 week = 35x
cost price for 1 week = 15x
profit = 35x-15x = 20x
additional cost of production = 11,000
this implies that 20x - 11,000  7800
 7800
20x - 11,000  7,800
 7,800
20x  7800+ 11000
 7800+ 11000
20x  18,800
 18,800
x  18800/2
 18800/2
x  9,400
 9,400
at least 9,400 packs have to be sold each week to make a profit of $7800
 
        
             
        
        
        
Answer:
Systematic sampling 
Step-by-step explanation:
An EPA contractor needing to test the concentration of a substance in ten samples out seventy samples provided form a single source at regular time intervals. 
For the contractor to effectively carry out the testing he has to employ a Non-probability system of sampling which is called Systematic sampling, because in systematic sampling we can assume the population size (x ) which in this case is 70 and the sample size( n ) to be 10 
He will have to select ;  ( x / n )^th of the sampling frame for best results 
 
        
             
        
        
        
We have that
scale factor=1 in/2.5 miles
<span>the actual area of a lake is 12 square miles
</span>we know that
[area on the map]=[scale factor]²*[area actual]
[area on the map]=[1/2.5]²*[12]-----> 1.92 in²
the answer is
1.92 in²