Each triangular face of the pyramid of Peace of Kazakhstan is made up of 25 smaller triangles as…

Each triangular face of the pyramid of Peace of Kazakhstan is made up of 25 smaller triangles as shown in figure below: Using the above information and concept of determinant answer the following question: If $(1,2)$ and $(3,6)$ are the coordinates of the two vertices of one of the smaller triangles and its area is 5 square cm, then find the equation of line on which the third vertex of the triangle lies.