Question 151407
300=r(t+2)
r=300/(t+2)
280=(r+20)t 
280=(300/(t+2)+20)t
280=300t/(t+2)+20t
280=(300t+20t(t+2))/(t+2)
280(t+2)=300t+20t^2+40t
280t+560=340t+20t^2
20t^2+340t-280t-560=0
20t^2+60t-560=0
20(t^2+3t-28)=0
20(t+7)(t-4)=0
t-4=0
t=4 hours for the express train
280=4(r+20)
280=4r+80
4r=280-80
4r=200
r=200/4
r=50 mph is the rate of the freight train.
proofs:
300=50(4+2)
300=300
280=(50+20)*4 
280=70*4
280=280