Hey there!
The definition of a scalene triangle is a triangle that has no equal sides, meaning that there cannot be a line of symmetry. A line of symmetry would be contained in a triangle that's an equilateral triangle, for example, which has three even sides. But since there are no even sides, there's no way for the triangle to be split in half evenly.
Your answer will be "never."
Hope this helped you out! :-)
