There are stools and chairs in the room. Each stool has $$3$$ legs, and each chair has $$4$$ legs. Altogether there are $$17$$ legs. How many chairs are there in the room? 
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If there are five stools, the chairs have $17-3\times5=2$ legs, which is not applicable. If there are four stools, the chairs have $17-3\times4=5$~ legs, which is also not applicable. If there are three stools, the chairs have $17-3\times3=8$ legs, which implies that there are $8\div4=2$ chairs and is applicable according to the question. 