Question 836146
LET X BE THE SPEED OF THE EAST BOUND TRAIN
LET X-20 BE THE SPEED OF THE WEST BOUND TRAIN
4[X+(X-20)]=640
4[2X-20]=640
8X-80=640
8X=640+80
8X=720
X=720/8
X=90 MPH FOR THE EAST BOUND TRAIN
90-20=70 MPH FOR THE WEST BOUND TRAIN
PROOF:
4[90+70]=640
4*160=640
640=640