(a) Find the equation of the line that passes through the origin and the point of intersection of the lines \( x + 2y = 7 \) and \( x - y = 4 \). (b) The ratio of an interior angle to an exterior angle of a regular polygon is 4: 1. Find the: (i) number of sides; (ii) value of the exterior angle; and (iii) sum of the interior angles of the polygon.