There are two cheap hotels ,but failing either of these,you may go back to where you were before

是“要是(两家中有)任何一家不行”之意啊.你没错!不是“要是两家都不行”!可是朗文词典上翻的是要是两家都不行明白了！原因是："failing either of these” 虽语法机构上不是否定式，但 fail 被视为是个否定词(见英英词典的解释)。所以，如果用 failing both of these 则反成半否定了--即一家可以，另一家不行，那后半部分逻辑上就不通了。换句话说，如果为“要是(两家中有)任何一家不行”则 “you may go back to where you were before” 说不通。在这个地方，词典对，我们理解错。参考：Both students were not strongly motivated. (正确意义：不是两个学生都目的明确、干劲十足。)All students were not from Japan. (不是所有学生都来自日本。)