Hi,
average income is approximately $45,000/year in this state, with a SD of about $9000.
using a normal distribution to approximate values that% of houseolds lie
1-.89 = .11, .11/2 = .055 Excel NORMSINV(.055)gives z = 1.59819
1.59819 = (X -45000)/9000
X = 1.598*9000 + 45000 = $59,382
and
-1.59819 = (x -45000)/9000
x = -1.598*9000 + 45000 = $30,618