If the force of friction resisting the students push is 4 N what is the net force acting on the board if the student is applying 10 N of force?

Net force is the total amount of force present, regardless of direction. Assuming that the forces given are the only forces acting on the object (as in, gravity, air resistance, etc. are excluded), then you would simply add those forces in order to get the answer. Thus, the correct answer is 14N.