Answer:
1 < x < 13
Explanation:
The longest leg of a triangle must be less than the sum of the shorter legs.
c < a + b
If the third piece is the longest leg, then:
x < 6 + 7
x < 13
If the 7-ft piece is the longest leg, then:
7 < 6 + x
x > 1
Therefore, the third leg is between 1 ft and 13 ft.