To discover the unit rate we need to know what it is we're pricing. The question lists a number of amounts in money, but what is the money buying. Is it fuel? Rolls of wallpaper? Sacks of potatoes? Crates of beer?
For example, 3 rolls of wallpaper costs $4.50; what is the unit price? The price of one roll is 4.50/3 = $1.50. The unit price (the price of one roll) is $1.50. Another example: a 500g box of cornflakes costs $2.50. What is the unit price, i.e., the cost per gram? The unit price is 2.50/500=0.5 cents per gram. Another example: a Thanksgiving turkey weighing 11 pounds cost $27.50, what is the cost per pound? 27.50/11=$2.50 per pound. Another example: my car can travel 300 miles on 12 gallons of fuel, what is the fuel consumption rate? How many miles per gallon? 300/12=25 miles per gallon.