A pair of table tennis rackets is 30 yuan, and a table tennis ball is 2 yuan. Xiaohua bought a pair of table tennis rackets with 50 yuan, and the rest of the money is used to buy table tennis balls. How many can you buy?
一副乒乓球拍30元，一个乒乓球2元．小华用50元买了一副乒乓球拍，剩下的钱买乒乓球，能买多少个？
<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>