Some language guides will tell you that 'farther' should be used for distance and that 'further' should be used in the sense of 'moreover', these words have been interchangeable for many, many years. Even the Old English origin for both words translates as 'to a great distance or long ago'. The Greek translation for both is 'across or beyond'

This would be something that goes along with your class. You could get the website from your teacher to begin.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Ireland is further west than Portugal.

Which is futher away will depend on where you are starting from. Compared to each other, Denver is further north and further west and Dallas is further south and further east.