Answer: The length of the third side is greater than 4 ft and less than 20 ft.
Step-by-step explanation: Given that two sides of a triangle have lengths 8 ft and 12 ft.
We are to describe the possible lengths of the third side.
Let x ft be the length of the third side of the triangle.
We know that
the sum of the lengths of any two sides of a triangle is always greater than the third side.
So, we must have
![8+12>x\\\\\Rightarrow 20>x\\\\\Rightarrow x<20~~~~~~~~~~~~~~~~~~~~~~~~~(i)](https://img.qammunity.org/2019/formulas/mathematics/high-school/uiqfagss7ssm051e076s66jyjqo0mxlcwu.png)
Also,
![12+x>8\\\\\Rightarrow x>8-12\\\\\Rightarrow x>-4~~~~~~~~~~~~~~~~~~~~~~~~~(ii)](https://img.qammunity.org/2019/formulas/mathematics/high-school/s3ciw3yyd689k3wf99kceydmr86qg72qt4.png)
and
![8+x>12\\\\\Rightarrow x>12-8\\\\\Rightarrow x>4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(iii)](https://img.qammunity.org/2019/formulas/mathematics/high-school/sq28xx0i2yqvtgcsf44p5upkw3fbs6o5iw.png)
From inequalities (i), (ii) and (iii), we get
![4<x<20.](https://img.qammunity.org/2019/formulas/mathematics/high-school/u1z8twkyv5j4o4yw6vbj3ds4fr5cjdls5m.png)
Thus, the length of the third side is greater than 4 ft and less than 20 ft.