Question 558130
You almost had it, and then lost your sense of direction.
You had {{{D[1]/5 = D[2]/9+144}}} and you were saying it was the same distance both ways.
So you could have written {{{D/5=D/9+144}}}
Having fractions/denominators makes it look hard, but you could have solved it to find
D=1620 km
Now you have the distance. You already had the times. 
The only question is the average speed in the outbound trip. I believe outbound is the trip going out there, to Moscow, so the time was 5 hours and the speed was 1620 km/5 h = 324km/h