since x (mean) is equal to 58 and the standard deviation is equal to 6-
x-s=52
x+s=64
x-2s=46
x+2s=76
x-3s=40
x+3s=76
therefore 64 is 1 (one) standard deviation above the mean from x+s, so 50%+34%(one standard deviation above)= 84%
the mean is the central line on the normal...