The unit price of a basketball is 40 yuan, and a football is 20 yuan more expensive than a basketball. The money Mr. Li brings can buy 30 basketballs. If you use this money to buy footballs, how many can you buy?
一个篮球的单价是40元，一个足球比一个篮球贵20元．李老师所带的钱正好能买30个篮球，如果用这些钱买足球，能买多少个？
<gadget id="calculator">40 * 30</gadget>
<output>1_200</output>

<gadget id="calculator">20 + 40</gadget>
<output>60</output>

<gadget id="calculator">1_200 / 60</gadget>
<output>20</output>

<result>20</result>