Find the mean for the following data: 

Marks $\left(x\right)$	$2$	$3$	$$$4$	$5$	$6$	$7$	$8$	$9$	$10$	$11$	$12$	$13$	$14$	$15$	$16$
Frequency $\left(f\right)$	$1$	$6$	$6$	$8$	$8$	$2$	$1$	$4$	$0$	$2$	$1$	$0$	$0$	$0$	$1$

 

The mean of a data set comprising of $\mathrm{16}$ observations is $\mathrm{16}$. If one of the observation value $\mathrm{16}$ is deleted and three new observations valued $3,\; 4$ and $\mathrm{5}$ are added to the data, then the mean of the resultant data is

If for some $x\in R$, the frequency distribution of the marks obtained by $20$ students in a test is:

Then the mean of the marks is :