when using y2-y1/x2-x1, you would get 8-(-3)/5-5. This simplifies to 11/0, which means that the line would have 0 slope. A line with 0 slope is a horizontal line.
Adding the two equations 3x + 6y + 3x - 6y = 36+0 6x = 36 x = 6 . subtracting second equation from first (3x + 6y ) - (3x-6y) =36 -0 12y = 36 y = 3 . therefore x = 6 and y = 3 (6,3)