Answer: The equation a+b+c=240 degrees is not true for any triangle, since the sum of the angles of a triangle is always 180 degrees. However, it could be true for a quadrilateral, which has four angles. One way to explain why a+b+c=240 degrees is to use the fact that opposite angles of a cyclic quadrilateral (a quadrilateral that can be inscribed in a circle) are supplementary, meaning they add up to 180 degrees. If we label the opposite angle of c as d, then we have c+d=180 degrees. Subtracting c from both sides, we get d=180-c. Then, adding a+b to both sides, we get a+b+d=240-c+c, which simplifies to a+b+c=240 degrees. Another way to explain why a+b+c=240 degrees is to use the fact that an exterior angle of a triangle is equal to the sum of the opposite interior angles. If we extend one side of the triangle and label the exterior angle as e, then we have e=a+b. Then, adding c to both sides, we get e+c=a+b+c. Since e+c is an exterior angle of another triangle formed by extending the side, it is equal to 180 degrees. Therefore, we have 180=a+b+c, which implies that a+b+c=240 degrees.