The Z-score formula states that
[tex]Z=\frac{x-\mu}{\sigma}[/tex]
Where x is the value of the variable, mu is the mean of the distribution, and sigma is the standard deviation.
The value of Z defines an area below the curve that represents a certain percentage of the total data (100%), in a diagram
Therefore, we need to find a value of Z such that it covers 100%-10.38%=89.62% of the total data. This value can be found using a Z-score table of cumulative probability.
The Z-value that corresponds to 89.62% is Z=1.26
Then, solving the equation for x,
[tex]\begin{gathered} Z=1.26,\mu=115,\sigma=19 \\ \Rightarrow x=Z\sigma+\mu \\ \Rightarrow x=1.26\cdot19+115=138.94 \\ \Rightarrow x=138.94 \end{gathered}[/tex]
The answer is $138.94