A basket of apples weighs 45 kilograms. After half of the apples are sold, the remaining apples weigh 24 kilograms. How many kilograms of apples are there? (Three methods are used, only list, no calculation)
一筐苹果连筐共重45千克，卖出苹果的一半后，剩下的苹果连筐共重24千克，求原来有苹果多少千克？(用三种方法，只列式，不计算)
<gadget id="calculator">45 - 24</gadget>
<output>21</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">21 / (1/2)</gadget>
<output>42</output>

<result>42</result>