Answer:
a = 14
Step-by-step explanation:
The mean is the sum of the values divided by the number of values.
[tex]\begin{array}{rcl}\text{Mean}&= &\dfrac{11 + 8 + 7 + a + 16 + 10}{6}\\\\\dfrac{52 + a}{6}& = & 11\\52 + a & = & 66\\a & = & 66 - 52\\& = & \mathbf{14}\\\end{array}[/tex]