x = 5 y = x - 8 Which of the following points x , y

Choice B is correct. A solution to a system of equations in the xy-plane is a point $\left(x,y\right)$ that lies on the graph of each equation in the system. The first equation given is $x=5$. Substituting $5$ for $x$ in the second given equation yields $y=5-8$, or $y=-3$. It follows that in the xy-plane, the point $\left(5,-3\right)$ lies on the graph of each equation in the system. Therefore, the solution to the given system of equations in the xy-plane is $\left(5,-3\right)$.

Choice A is incorrect. The point $\left(0,0\right)$ doesn't lie on the graph of either equation in the given system.

Choice C is incorrect. The point $\left(5,-8\right)$ doesn't lie on the graph of the second equation in the given system.

Choice D is incorrect. The point $\left(5,8\right)$ doesn't lie on the graph of the second equation in the given system.