Find the​ z-score for which a total probability of 0.86 falls more than z standard deviations​ (in either​ direction) from the mean.

Z-score = 0.1764 ≈ 0.18

Step-by-step explanation:

Z-score for Total probability of 0.86

This can found as shown below

P( Z < -Z ) + P( Z > Z ) = 0.86

= P ( Z < -Z ) + P ( Z < - Z ) = 0.86

=  P ( Z < - Z ) = 0.86 / 2 = 0.43

hence Z-score  = 0.1764  ( from standard Normal table )

the answer is (2x+8)²= 16