For the health and safety of students, the school provides each dormitory student with a water cup. Each cup is 3 yuan. Supermarket A offers a 10% discount. Supermarket B buys 8 cups and gets 1 free. The school needs to buy 180 cups. Where can I buy it cheaply? Some, how much cheaper?
为了学生的卫生安全，学校给每个住宿生配了一只水杯，每只水杯3元，A超市打九折，B超市买8只送1只，学校要买180只水杯，到哪家买便宜一些，便宜了多少元？
<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<gadget id="calculator">180 / 9</gadget>
<output>20</output>

<gadget id="calculator">180 - 20</gadget>
<output>160</output>

<gadget id="calculator">160 * 3</gadget>
<output>480</output>

<gadget id="calculator">486 - 480</gadget>
<output>6</output>

<result>6</result>