The Li family has 125 kilograms of coal, and the Zhang family has 83 kilograms of coal. If the Li family uses 2.8 kilograms of coal every day, but the Zhang family has been useless, how many days later will the two families have the same amount of coal left? (solution by equation)
李家有煤125千克，张家有煤83千克．若李家每天用煤2.8千克，而张家一直没用，多少天后两家剩下的煤一样多？(用方程解)
<gadget id="calculator">125 - 83</gadget>
<output>42</output>

<gadget id="calculator">42 / 2.8</gadget>
<output>15</output>

<result>15</result>