Answer
See below.
Work Step by Step
The mean of $n$ numbers is the sum of the numbers divided by $n$. The median of $n$ is the middle number of the numbers when they are in order (and the mean of the middle $2$ numbers if $n$ is even). The mode of $n$ numbers is the number or numbers that appear(s) most frequently. Hence here the mean: $\frac{212+222+222+231+235+250}{6}\approx228.667$, the median is the average of the middle $2$ in the sequence $212,222,222, 231, 235, 250$, which is: $(222+231)/2=226.5$, the mode is $222$. The range is the difference between the largest and the smallest data value. The standard deviation of $x_1,x_2,...,x_n$ is (where $\overline{x}$ is the mean of the data values): $\sqrt{\frac{(x_1-\overline{x})^2+(x_2-\overline{x})^2+...+(x_n-\overline{x})^2}{n}}$. Hence here the range is: $250-212=38$ and the standard deviation is: $\sqrt{\frac{(212-228.667)^2+(222-228.667)^2+...+(250-228.667)^2}{6}}\approx 12.023$
When every value of a data set is multiplied by a constant, the new mean, median, mode, range, and standard deviation can be obtained by multiplying each original value by the constant. Here the constant is $0.9$, hence the mean: $228.667\cdot 0.9=205.8$, the median: $226.5\cdot 0.9=203.85$, the mode: $222\cdot 0.9=119.8$, the range:$38\cdot 0.9=34.2$, and the standard deviation: $12.023\cdot 0.9=10.8207$.
