A 250-gram bag of high-calcium milk, the original price is 1.8 yuan per bag, and now the promotion is "buy 6 get 1 free", and the mother spent 32.4 yuan on it. How many bags of this milk can I buy at most?
一种250克一袋的高钙牛奶，原价每袋1.8元，现在促销"买6送1"，妈妈花了买32.4元，最多可以买这种牛奶多少袋？
<gadget id="calculator">32.4 / 1.8</gadget>
<output>18</output>

<gadget id="calculator">32.4 / 1.8 / 6</gadget>
<output>3</output>

<gadget id="calculator">18 + 3</gadget>
<output>21</output>

<result>21</result>