Question 13307
let the distance between perry ville & granite city be x miles.

THe time for train a to reach Granite city from perryvilleis x/64 hrs
and time for train b to reach perryville from granite is x/48 hrs
total time = x/64  + x/48  = 7/2 hrs (or 3.5 hrs 6 am to 9:30 am)
solving for x we get x = 96 miles