Question 1138407
The middle 15% is between 0.4250 and 0.5750, and this is z between -0.19 and +0.19
z=(x-mean)/sd
The mean is middle of 6 and 17 or 11.5

SD--0.19=(17-11.5)/SD
0.19 SD=5.5
SD=28.95 or 29