This Instructional Activity is a part of the Lesson 12, Unit 2, Grade 8. In this activity, they find that points (x,y) on this line are of the form (2s, s+1) where s is a (positive) real number. Make sure that students understand that the equation (y-1)/x = 1/2 is true if we take y-1 = s+1 and x = 2s. Also, emphasize the key role that dilations play in these arguments. The big take away from this lesson is that the structure of the coordinates of points on a line can be derived from properties of dilations.