Question 163720
390=3x+3(x+30)
390=3x+3x+90
6x=390-90
6x=300
x=300/6
x=50 kmh. is the speed of the freight train.
50+30=80 kmh. for the speed of the express train.
Proof:
390=3*50+3*80
390=150+240
390=390