If a train travels the distance between two cities $($from city$1$ to city$2)$ with constant speed of $60$ km$/$h$,$ it will get there $1$ hour late. If it travels the same distance with $80$ km$/$h it will get there half an hour early. What is the distance between two cities.

Hint:$$ Either way the distance traveled by the train is the same, so Delta X $($for V of $60$ km$/$h $)=$ Delta X $($for V of $80$ km$/$h $).$

Being $1$ hour late means t$1=$ t $+1($in hours$)$

Being half an hour soon means t$2=$ t $1/2($in hours$)$