The average (mean) of $3,5,6,8$, and $x$ is 7 . What is the value of $x$ ?
Since the average of 5 numbers is 7 , then the sum of the 5 numbers is $5 \times 7=35$.

Therefore, $3+5+6+8+x=35$ or $22+x=35$ and so $x=13$.

ANSWER: 13