Answer:
15 < n < 25
Explanation:
According to the triangle inequality theorem, any two sides lengths' sum should be greater than the third side. This also implies that to find the possible length of the 3rd side given other two sides (let two given sides be x and y), we can say that the 3rd side length will be between x+y and x-y.
Hence, we can say that n should be between 20+5 and 20-5.
So, 20 - 5 < n < 20 + 5, which is
15 < n < 25
This is the correct answer.