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What is the 17th term in the arithmetic sequence in which a6 is 101 and a9 is 83

Mrs. avila is buying a wallpaper border to go on all of her kitchen walls. she wants to buy 5 extra feet of wallpaper border than she needs to be sure she has enough. she buys 55.5 feet of the border. the store owner selling the border uses the width of mrs. avila's kitchen to determine that the length of her kitchen must be 14.5 feet.

Ineed to know how to write question one in mathematical terms