In an isosceles triangle, two sides are equal to each other. So, we know that the third side is either 6 or 15 inches.
If the third side is 6 inches, it would not make a triangle. The sum of any to sides of a triangle must be larger than the third side. However, 6+6 is LESS than 15, so 6 inches would not be the answer.
By process of elimination, the third side is 15 inches. Good luck!
