Abrick is resting on the surface of a flat board. as one end of the board is slowly raised, what change, if any, is there in the normal force exerted on the brick?

The normal force decreases, this is the frictional force. It will be counteracted by the force which accelerates the brick to slide downward opposite to the end where the board is raised. As the angle increases the force acting upon the brick opposite to the normal force will decrease.

i would think form in reponse to tensional forces

50 inches should be the resultant vector