Ivy can do a job in $$24$$ days and Kevin can do it in $$20$$ days. Now they\textquotesingle re working together. But in the middle of the job, Kevin takes some days off. If they finish the job by the end of the $$18^{}\text{th}$$ day, how many days does Kevin take off? 
Overseas Competition->Knowledge Point->Word Problem Modules->Work Word Problems->Collaborative Work Word Problems