Triangle Theorem, which three side angles form a triangle. 8,4,12.. 8,8,20.. 20,10,30.. or 10,20,15

The triangle theorem states that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side.

In this case, only the set of side lengths 8, 8, and 20 does not satisfy the triangle theorem because 8 + 8 = 16 which is not greater than 20.

Therefore, the possible triangle with side lengths 10, 20, and 15 forms a valid triangle according to the Triangle Theorem.