It says decreasing so you have to turn it into a percent (.06%) and then sub tract that from 1. After that you put that into an equation.
18 minutes because 6*2 is 12 and 3*6 is 18. it will take 6 minutes to do 4 problems, 9 minutes to do 6 problems , 12 minutes to do 8 problems, 15 minutes to do 10 problems, and 18 minutes to do 12 problems
A b and c are your variables
Hope this helps
Answer:

Step-by-step explanation:
From the question we are told that:
Mean 
Standard deviation 
Significance level 
Therefore
Confidence level 
From table 
Generally the equation for Z-score is mathematically given by



