Xiao Dingding took 68 yuan to the store and bought 2.5 kilograms of apples. It is known that the apples are 10.2 yuan per kilogram. How much money is left?
小丁丁带68元去商店买了2.5千克的苹果，已知苹果每千克10.2元，还剩下多少元？
<gadget id="calculator">10.2 * 2.5</gadget>
<output>25.5</output>

<gadget id="calculator">68 - 25.5</gadget>
<output>42.5</output>

<result>42.5</result>