Triangle inequality theorem states that the sum of the lengths of two sides of a triangle will always be more than the length of the third side.
Given the two sides of the triangle as 8 inches and 12 inches.
There sum would be 8 + 12 = 20 inches.
So, according to the theorem:
Sum of side measureing 8 inches and 12 inches must be more than x.
So, 8 + 12 > x.
20 > x
Therefore, x < 20.
So, x must be less than 20 inches.
Hope this helps you!