If the mean of observations x, x+3, x+5, x+7, ext{and } x+10 is 9, find the mean of the last three observations.

The sum of the five observations is $x + (x+3) + (x+5) + (x+7) + (x+10) = 5x + 25$. Given the mean is $9$, $(5x+25)/5 = 9 \implies x+5 = 9 \implies x=4$. The last three observations are $x+5 = 9$, $x+7 = 11$, and $x+10 = 14$. Their sum is $9 + 11 + 14 = 34$, and their mean is $34/3 = 11.33$.