Question 831739
Let h equal the time that the B to A train traveled.


A to B______________80______________(1/2)+h_____________(___)
B to A______________100_____________(h)_________________(___)
TOTAL___________________________________________________220



Use R*T=D to find expressions for each distance.


A to B______________80______________(1/2)+h_____________80(h+1/2)
B to A______________100_____________(h)_________________100h
TOTAL___________________________________________________220


EQUATION:  {{{80(h+1/2)+100h=220}}}.
Solve for h.  
-
80h+40+100h=220
8h+10h+4=22
18h+4=22
18h=18
{{{highlight(h=1)}}} hour, the B to A train.
The A to B train traveled {{{highlight(h=1&1/2)}}} hour.