A triangle has a perimeter 13. The two shorter sides have integer lengths equal to x and x + 1. Which of the following could be the length of the other side?

The measure of the third side of a triangle must lie between the sum and the difference of the other two sides. Using this fact along with the answer choices, we can eliminate the wrong answers. 

• Option A  cannot be correct because 4 would not be the longest side.(sides 4, 5, and 4)   

• Option B could be correct because the other two sides would be 3 and 4.  

• Option C cannot be correct because this third side would be greater than the sum of the other two sides.