Question 1033606
shorter delivery time will be on the left of the z scale, whilst longer times will be on the right side.  we are going to need to find out the numerical value for the last 10 percent on the right of the z scale, to do that, we will have to look up a z scale and find the number closest to 90 percent.

when we look on the z chart, the number closest to .9000 is .8997, with the z score of that being  z = 1.28

using that number we will multiply the z score by S (standard deviation) then add the mean to get the number of minutes.

1.28 x 3 then + 22 = 25.84 minutes.   assuming I understood the whole "10% of the customers" correctly