1303/12.8 is the answer for that one which it should land in the middle of the line!
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!