Let t = travel time at 58
and
(6-t) = travel time at 49
distance at 58 + distance at 49 = 325.5 mi
58t + 49(6-t) = 325.5
58t + 294 - 49t = 325.5
9t+294 = 325.5
9t =31.5
T = 31.5/9 = 3.5 hours at 58 mph
6-3.5 = 2.5 hours at 49 mph
Check:
58*3.5 = 203
49*2.5= 122.5
203+122.5 = 325.5