The correct answer is: 11+b
In this case 
 is a variable.
 is a variable.
11 is a number.
Since it is asking for the sum then that means you must add those two together.
This means that the sum of 11 and 
 means that you have to add the two factors.
 means that you have to add the two factors.
Therefore, the sum of 
 and 11 is:
 and 11 is:
11 + 

Hope this helps! :3