Question 23078
Draw the picture.
East train data:  distance = x; rate=30; time = x/30
West train data:  distance = 280-x; rate = 40; time = (280-x)/40
EQUATION:
Time East = Time West
x/30 = (280-x)/40
40x = 30(280-x)
40x = 30(280)-30x
70x =30(280
  x = 3(40)
  x = 120 mph
Therefore time = x/30 = 120/30= 4 hours

Cheers,
Stan H.