Some students are going to an amusement park. If each student carries $9$ bottles of water in his or her backpack, there will be $2$ students carrying nothing; if one of the students carries $2$ bottles of water and the rest students carry $8$ bottles each, all the bottles of water can be carried to the park. There are~\uline{~~~~~~~~~~}~bottles of water in total that need to be carried. 
Overseas Competition->Knowledge Point->Word Problem Modules->Distribution Problems->Distribution Conversion Problems
Solve the problem as a problem of surplus and shortage. If each student carries $9$ bottles, there will be a shortage of $9\times2=18$ bottles;  if each student carries $8$ bottles, there will be a shortage of $8-2=6$ bottles. Therefore, there are $(18-6)\div(9-8)=12$ students and $12\times9-18=90$ bottles of water. 