Store e offers a book that karen wants for 20% off its regular price of $15.00. store f sells the same book for $15, before a $3.00 mail-in rebate. where should karen purchase the book? explain your reasoning.

Atrain leaves little? rock, arkansas, and travels north at 90 kilometers per hour. another train leaves at the same time and travels south at 80 kilometers per hour. how long will it take before they are 680 kilometers? apart?