Uncle Wang’s family has 18 ducks, which are 12 more than chickens. To make the number of ducks 8 more than chickens, how many chickens should Uncle Wang buy.
王伯伯家养了18只鸭，比鸡多12只，要使鸭的只数比鸡多8只，王伯伯家还要买多少只鸡．
<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<result>4</result>