Let

denote the number of minutes spent brushing his teeth, and let

be the mean and

the standard deviation for this distribution.

The z-score corresponding to this probability is approximately

, which means

Next, (note the sign change)

The corresponding z-score is approximately

, so you have

Solving the two equations for

and

, you'll find that the mean is approximately

and the standard deviation is approximately

.
Answer:
47.25 + 23.75 = 71
Step-by-step explanation:
Dan zack brian
zack dan brian
brian dan zack
zack brian dan
brian zack dan
dan brian zack
6 different orders
Hope this helps!!