The equation you use for the slope of this kind of problem is (y2-y1)/(x2-x1). x1 is the first X coordinate, x2 is the second, y1 is the first y coordinate, y2 is the second.
(5-3)/(2-2) 2/0 This equation has an UNDEFINED SLOPE, as it is just a vertical line.
15+c=17.50
First you subtract 15 by 15 because you switch operations from adding to subtracting then you would put C under it
Second subtract 17.50 and 15 and that is 2.50 so C= 2.50
