20% of 150 is 30 
Change the percentage into a decimal by dividing it over 100:
20 / 100 = 0.2
Multiply:
0.2 × 150 = 30
        
             
        
        
        
To solve this, first we calculate all the total cost of
the items that is:
total cost = $14.96 + $19.87 + $5.37
total cost = $40.20
 
So we see that the actual cost is similar with the
estimate so his calculation is reasonable.
 
        
             
        
        
        
Answer: y = x^2 - 2 does not represent a linear function because the squared exponent above the variable makes that equation quadratic. Quadratic equations look like parabolas on a graph, rather than lines.