Candy can do a job in 20 days, and David can do the same job in 25 days. Now they\textquotesingle re working together, but David takes some days off in the middle of the job. If they finish the job by the end of the $12th$~day, how many days does David take off?（⭐⭐⭐⭐⭐） 
Overseas Competition->Knowledge Point->Word Problem Modules