A snail is climbing up from the bottom of a $15$-meter-deep well. It climbs up $3$ meters during the daytime, and slides down $1$ meter every night. How many days will it take to get out of the well? 
Overseas Competition->Knowledge Point->Word Problem Modules->Periodic Problems->Snail Climbing out of Well Problems
It climbs up $$3-1=2$$ meters actually everyday. It takes $$12\div 2 +1=7$$ days in total, and in the last day, it climbs up $3$ meters. 