Написать, какое путешествие будет дешевле, быстрее или дороже - на автобусе, на поезде, по морю или на самолёте.
Например,
Travelling by bus is cheaper than travelling by sea. (Путешествовать на автобусе дешевле, чем по морю).
Travelling by plane is faster than travelling by train.
Travelling by sea is more expensive than travelling by bus.
Travelling by train is cheaper than travelling by plane.
Travelling by train is faster than travelling by bus.