Question 61278
490=(R-15)*6+R*4
490=6R-90+4R
490=10R-90
10R=490+90
10R=580
R=580/10
R=58 MPH FOR 4 HOURS FOR THE SOUTH BOUND TRAIN 
THUS THE NORTH BOUND TRAIN WAS TRAVELING 
58-15=43 MPH FOR 6 HOURS
PROOF
490=43*6+58*4
490=258+232
490=490