Answer: 11.5%
Explanation:Since 1 minute = 60 seconds, we multiply 12 minutes by 60 so that 12 minutes = 720 seconds. Thus, we're looking for a probability that the auditor will spend more than 720 seconds.
Now, we get the z-score for 720 seconds by the following formula:

where

So, the z-score of 720 seconds is given by:

Let
t = time for the auditor to finish his work
z = z-score of time t
Since the time is normally distributed, the probability for t > 720 is the same as the probability for z > 1.2. In terms of equation:

Hence, there is
11.5% chance that the auditor will spend more than 12 minutes in an invoice.
This equation can have a number of solutions. Typically when solving a two-variable equation, you are looking for the slope intercept form of the line. In this case that is:
y = 3x - 1
The equation for a line is mx + b = y where m is the slope and b is the y intercept. To find the slope, we need to use the equation
.



Therefore, m is equal to -1. Normally, we would then have to plug in m and one of the points to find b. However, because the point (0,5) is the y-intercept (the y-intercept is the point on the line where x is equal to 0), we can skip this step and go straight to forming the final equation, which is
.