Uncle Wang’s family raised 7 chickens, the number of ducks was three times that of chickens, and the number of rabbits was 21 more than the number of ducks. How many rabbits did Uncle Wang raise?
王叔叔家养了7只鸡，鸭的数量是鸡的3倍，兔子的数量比鸭的数量多21只，王叔叔养了多少只兔子？
<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">21 + 21</gadget>
<output>42</output>

<result>42</result>