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The owner of a bicycle store had a sale on bicycles(two-wheelers) and tricycles(three-wheelers). Each cycle had two pedals. When he counted the total number of pedals of the cycles, he got 50 . When he counted the total number of wheels of the cycles, he got 64 . How many tricycles were offered in the sale? 
Overseas Competition->Knowledge Point->Word Problem Modules->Equation Word Problems
$50\div 2=25$  let $x$ be the number of bicycles, $y$ be the number of tricycles  $2x+3y=64$  $x+y=25$ 