You can
put this solution on YOUR website!d=distance t=time v=velocity
d=tv
Let t=time of 1st train
Let t-4=time of 2nd train
for the 1st train d=tv=48t
for the 2nd train d=tv=68(t-4)
they both travel the same distance therefore: 48t=68(t-4)
48t=68t-272
add 272 and -48t to both sides: 272=20t
t=13.6hrs
t-4=9.6hrs time it took train b to catch up to train a
EdJones