Question 1200844
top 15% would be those with scores above 932.243.
calculator i used can be found at <a href = "https://davidmlane.com/hyperstat/z_table.html" target = "_blank">https://davidmlane.com/hyperstat/z_table.html</a>
here's a display of the results.
<img src = "http://theo.x10hosting.com/2023/030901.jpg">


if you use z-cores, you would do the followng.
the z-score with 15% of the area under the normnal distribution cure to the right of it is equal to 1.03643338.
z-score formuls is z = (x - m) / s
z is the z-score
x is the raw score
m is the mean
s is the standard deviation
formula becomes 1.03643338 = (x - 840) / 89.
solve for x to get x = 89 * 1.03643338 + 840 = 923.2425708.
round to 923.243 as shown in the calculator.