### Instruction: The sequence $2, 7, 12, a, b, 27$ is arithmetic. What is the value of $a + b$?### Response: An arithmetic sequence is a sequence of numbers where each term is obtained by adding a constant difference to the previous term.
To find the difference, I can subtract any two consecutive terms, for example $7 - 2 = 5$ or $12 - 7 = 5$.
So the difference is $5$ and I can use it to find $a$ and $b$.
To get $a$, I need to add $5$ to $12$, so $a = 12 + 5 = 17$.
To get $b$, I need to add $5$ to $a$, so $b = a + 5 = 17 + 5 = 22$.
Therefore, $a + b = 17 + 22 = 39$.