Because there is no intersection between the straight line and the straight line y=2x-3, the straight line is parallel to y=2x-3 and set to Y = 2x+b.

And it intersects with the straight line y=6-x at point A (5, k), that is, the straight line intersects with point A (5, 1), so b=-9.

So the relationship of this function is y=2x-9.