Question 1037473
The sum of the lengths of two sides must be greater than the third side.
To the nearest tenth, the third side could be 3.1 inches, which is just enough to make a triangle with 12 inches and 15 inches.  12+3.1>15,1 
Alternatively, it could be 26.9 inches, were the other two lengths nearly a straight line. 12+15>26.9
The answer to the question is not 23.8 inches, the difference between the two, but 23.9 inches, because anything slightly greater than 3 inches or slightly less than 27 inches would work, and rounding it higher would be a tautology.  A case may be made for either length.