It’s the first one!! :)))
Answer:
4. 6/15
Step-by-step explanation:
5. 5/3 is the an answer
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: $170
15% off 100 is $15 x2 is 30