A basket of apples weighs 56 kilograms. First half of the apples are sold, and then half of the remaining apples are sold. At this time, the weight of the basket is 17 kilograms. How much does the empty basket weigh?
一筐苹果连筐重56千克，先卖掉一半的苹果，再卖掉剩下苹果的一半，这时连筐还重17千克，空筐重多少千克？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * (1/2)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/2) + (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">39 / (3/4)</gadget>
<output>52</output>

<gadget id="calculator">56 - 52</gadget>
<output>4</output>

<result>4</result>