Answer:the 3rd length could be 10 if the triangle is a right angled triangle,and 6 and 8 are the opposite and adjacent sides.
Explanation:
If the triangle is a right angled triangle with 6 and 8 as the opposite and adjacent sides, then they missing side is there hypotenuse.this can be gotten using Pythagoras rule
Hypotenuse=√(8^2+6^2)
Hypotenuse=√(8x8+6x6)
Hypotenuse=√(64+36)
Hypotenuse=√(100)
Hypotenuse=10