I think this means to find the mid-point(?) of the line which by doing that you take both x-values and you add them and then divide by two, and then you take both y-values and add them and then divide by two. So you have: (1+-4)=-3, (-3/2)=-1.5
In the ratio 2:3 going to 28:? there is a pattern. You multiply 2 by 14 to get to 28, so if you multiply 3 by 14 you get 42. Add 42 to 28 for the total amount of students in class!
