Answer: +17
Step-by-step explanation: The common difference is the number that your repeatedly adding or subtracting to reach the next term.
Here, notice that your adding 17 to get from 31 to 48.
In the same way, your adding 17 to get from 48 to 65.
Your also also adding 17 to get from 65 to 82.
Since you keep on adding 17, the common difference is +17.