I’m pretty sure it’s 60 but I’m not 100% sure so I’m sorry if it’s wrong
        
             
        
        
        
(12)(20)= 240 
The answer is going to be B. 240 sq ft
        
                    
             
        
        
        
Answer 
(a)

(b)

Step-by-step explanation:
Remember that when you want to solve a problem like this, you express the equation as following 

So, if you know the inverse of    then
   then 

For this case 

Now for this case the inverse of A would be 

Then when you multiply with the vector solution 

So from that information you can conclude that  the solution to the system of equations is  x = 500/7   y = 2400/7  and z = 2700/7 
 
        
             
        
        
        
Answer: 
choice B) yes; only one range value exists for each domain value---------------------------------
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Explanation:
The inputs are x = -3, x = -1, x = 1, x = 5. They are the first coordinate listed of each point. We don't have any x values repeating so this means we have a function. Each input leads to exactly one output which is what 
choice B is stating. The domain is the set of allowed inputs, or x values. The range is the set of possible y outputs. 
If we had something like (1,2) and (1,5) then the input x = 1 leads to more than one output (y = 2 and y = 5). This example means we don't have a function
If you graph the points (-3, -2), (-1,0), (1,0) and (5,-2) as shown in the attached image, then you'll notice that it is impossible to pass a single line through more than one point. Therefore this graph passes the vertical line test visually proving we have a function. 
Going back to the example with (1,2) and (1,5), plotting these two points leads to the vertical line test failing implying we don't have a function.