I would first ask the student to draw out a heptagon to check if they know what the shape is.(white board - drawing shape)
Next i will ask them to start at one edge of the shape and ask them to draw a line to each other edge, this would lead to 4 triangles being formed.(white board - drawing straight lines)
Then i would tell the student the triangle fact; "angles in a triangle add up to 180 degrees", since there are 4 triangles in this hexagon, all the angles in the regular hexagon would add up to 4*180 = 720 degrees(white grid multiplication) (ask the student to show me how they would calculate)(emphasise the importance of showing workings)
As an extension i would ask the student to calculate what the angle of each side would be in a regular hexagonAnswer: 720/6 = 120 degrees(white board - long division)
Emphasise the importance to units (e.g. Degrees)
As a further extension, i would ask the student what the to name the angle (120 degrees is an obtuse angle)