Chebyshev's Rule states that at least 1-1/k2 of data from a sample must fall within "k" standard deviations from the mean. Since we already know the percentage of data is 89%, we can easily find "k":
1-1/k2 = 0.89
k2-1 = 0.89k2
-1 = -0.11k2
9 ≈ k2
k ≈ 3
Therefore, we can expect to find at least 89% of the prices within 3 standard deviations of the mean. This interval would be between 168000-3(6000)=$150000 and 168000+3(6000)=$186000.
Hope this helped!