Same direction
Erin -- 2 Miles -- School -- 4 Miles -- Janelle
Opposite directions
Janelle - 6 Miles -- Erin -- 2 Miles -- School
Now what?
Right, so what's your plan?
Stare at my little diagrams until it soaks in.
You MAY wish to draw a different diagram.
1) Draw a big circle - Label it "Janelle"
2) Draw a smaller concentric circle inside the larger circle. - Label it "School"
3) In the center of both circles (that is just one place) put Erin.
4) From Erin, draw a little arrow to the School circle and call it "2 miles"
5) From Erin, draw a little arrow to the Janelle circle and call it "6 miles"
In your mind, move the little arrows around their respective circles. Pretty much like an analog clock. The difference of their endpoints is the distance from Janelle to School. Does it have a maximum value? Does it have a minimum value? Think about my original diagram and it should come to you after enough staring and pondering.