Monday....uh oh

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I am Phebe, again, I want to ask how to know which gear i should do with this?
http://photos-542.ak.facebook.com/ip005/v17/36/61/9217352/n9217352_31478542_5663.jpg

http://photos-543.ak.facebook.com/ip005/v17/36/61/9217352/n9217352_31478543_8773.jpg


and I don't have any part located at the front frok that can release.....

and Monday I need to ride 7 miles, it is hot and dry here...here is TEXAS, WACO!!!

and I've never done such a long ride, what can I do ?