Answer:
z = 0.80
Explanation:
You want the value of z such that p(-z < X < z) = 0.5762 for a normal distribution.
Tails
The area outside the region of interest will be split evenly between the two tails. That is, the lower tail will hold (1 -0.5762)/2 = 0.2119 of the area of the distribution. The required value of z will be the magnitude of the Inverse CDF function for this value.
Inverse CDF
The attached calculator shows the required value of z is about 0.80.