Answer: The range of possible values for the third side of the triangle is: 12.5 < x < 18.9. This is because the length of any side of a triangle must be greater than the difference between the other two sides and less than the sum of the other two sides. Therefore, we have:
- 12.5 < 31 - x (from x > 18.9)
- 12.5 + x > 31 (from x < 18.9)
- 18.5 < x < 18.9
Rounding to one decimal place, we get 12.5 < x < 18.9.