A z-score<span> is the number of standard deviations from the mean a data point is.
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Standard deviation explains by how much the members of a group differ from the mean value for the group.
Using the z-score formula:
                                           z = ( x  - μ ) ÷ σ
Where;
            x = score
            μ = Mean
            σ = Standard deviation 
Z- Score (Tara) = ( 52 - 64 ) ÷ 8 
                         = - 12 ÷ 8 
                         = - 1.5 
Z- Score (Jamal)  = ( 82 - 64 ) ÷ 8 
                             = 18 ÷ 8 
                             = 2.25 
Z- Score (Samuel) = ( 66 - 64 ) ÷ 8 
                               = 2 ÷ 8 
                               = 0.25
        
             
        
        
        
Your answer for this problem would be 76-89+ 38, which equals negative 48
        
             
        
        
        
No this is not a triangle. With these lengths 
 
        
                    
             
        
        
        
y - 3x = 7
can be written as
y = 3x + 7
For every value of x there is a unique value of y.  For example when x = 0 y = 3(0) + 7 = 7
Yes it is a function. 
In particular it is a one-to-one function.