Three boxes under my stairs contain apples or pears or both. Each box contains the same number of pieces of fruit. The first box contains all twelve of the apples and one-ninth of the pears. How many pieces of fruit are there in each box? 
Overseas Competition->Knowledge Point->Word Problem Modules->Equation Word Problems->Word Problems for Linear Equations with One Variable
$(1-\frac19)\div2=\frac49$, $\frac49-\frac19=\frac13$, $12\div\frac13=36$, $36\times\frac49=16$. 