Answer:
purple
Step-by-step explanation:
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
.
Your picture is a bit blurry. What is the equation on WX and on ZY?