How to translate a problem into an equation when dealing with perimeter and trying to find the length?

It costs 4.25 for 1 pound of roast beef. how much will it cost to purchase 2.5 pounds of roast beef? round to nearest cent

Two cars which are 40 miles apart start moving simultaneously in the same direction with constant speeds. if the speed of the car which is behind is 56 mph and the speed of the other car is 48 mph, how many hours will it take for the car which is behind to catch up the car ahead of it?

Atorch and a battery cost 2.50 altogether. the torch costs 1.50 more than the battery. what fraction of the total price is the torch? give your answer in its simplest form.