### Instruction: The mean of $5,8$ and $17$ is equal to the mean of $12$ and $y$. What is the value of $y$?### Response: To find the mean of a set of numbers, I need to add up all the numbers and divide by the number of numbers.
So, the mean of $5,8$ and $17$ is $\frac{5+8+17}{3} = \frac{30}{3} = 10$.
The mean of $12$ and $y$ is $\frac{12+y}{2}$.
Since the means are equal, I can write an equation: $\frac{12+y}{2} = 10$.
To solve for $y$, I can multiply both sides by $2$ and subtract $12$: $y = 2 \times 10 - 12 = 20 - 12 = 8$.
Therefore, the value of $y$ is $8$.