Atrain leaves sandy traveling west at 60 miles per hour. an hour later, another train leaves sandy traveling east at 80 miles per hour. when are the two trains the same distance from sandy?

D1 = d2 
60 + 60t = 80t 
20t = 60 
t = 3 h.

They want to know when the trains are the same distance away from Sandy.  However it is important to note that they are moving in opposite directions so we really are dealing with only magnitude and not direction

a=60t, b=80(t-1), since a=b we can say:

80(t-1)=60t

80t-80=60t

20t-80=0

20t=80

t=4

So 4 hours after the first train left and 3 hours after the second train left, the two trains are the same 240 miles away from Sandy.

The expression of this would be 3.75x+y= 23