题目

Joe Simpson and Simon Yates were the first people to climb the West Face of the Siula Grande in the Andes mountains. They reached the top   41    , but on their way back conditions were very  42   . Joe fell and broke his leg. They both knew that if Simon   43    alone, he would probably get back  44   . But Simon decided to risk his   45    and try to lower Joe down the mountain on a rope(绳). As they   46    down, the weather got worse. Then another   47    occurred. They couldn’t see or hear each other and,   48   , Simon lowered his friend o8．为节约用水，某市居民生活用水按级收费，具体收费标准如下表： 用水量（吨） 不超过17吨的部分 超过17吨不超过31吨的部分 超过31吨的部分 单位（元/吨） 3 5 6.8设某户居民家的月用水量为x吨（17＜x≤31），应付水费为y元，则y关于x的函数表达式为y=5x-34．