How many miles can you walk in 4 1/2 hours

We cannot do this question for you as it requires information from you, the questioner. Unless there is a unit rate involved, it's best for you to use your own statistics to answer your question.

The average person can walk one mile in 20 minute. 
So 4 1/2 hours equal 270 minutes. Divide this by 20 minutes and you should have 13.5 which means that you would walk 13 1/2 miles in 4 1/2 hours.
Hope this helps you!