Watermelon costs 2 yuan per 3 kilograms, and cantaloupe costs 2 yuan per kilogram. Mom plans to buy 12 kilograms of watermelon and 5 kilograms of cantaloupe. How much should I pay?
西瓜每3千克2元钱，哈密瓜每千克2元钱，妈妈打算买12千克西瓜和5千克哈密瓜，应付多少钱？
<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<gadget id="calculator">8 + 10</gadget>
<output>18</output>

<result>18</result>