Line segment ac has endpoints a (-1,-3.5) and c (5,-1). point b is on line segment ac and is located at (0.2,-3). what is the ratio of ab/bc

The first thing you should do in this case is find the distance between the points.
 The distance between two points can be thought of as a line.
 To find the length of this line, you can use the distance formula:
 d = √ (x2 - x1) ^ 2 + (y2 - y1) ^ 2
 We have then:
 AC distance:
 AC = root ((5 - (-1)) ^ 2 + (-1 - (-3.5)) ^ 2) = 6.5 units
 AB distance:
 AB = root ((0.2 - (-1)) ^ 2 + (-3 - (-3.5)) ^ 2) = 1.3 units
 BC distance: 
 BC = 6.5-1.3 = 5.2 units
 
 
 The ratio is:
 AB / BC = (1.3) / (5.2)