The school bought large and small blackboards for a total of 300 yuan. The big blackboard was 22.5 yuan each, which was 2.5 yuan more expensive than the price of 2 small blackboards. The big blackboard bought 8 pieces, and how many small blackboards did you buy?
学校添置大小黑板共用去300元，大黑板每块22.5元，比2块小黑板的价钱还贵2.5元，大黑板买了8块，小黑板买了多少块？
<gadget id="calculator">22.5 * 8</gadget>
<output>180</output>

<gadget id="calculator">300 - 180</gadget>
<output>120</output>

<gadget id="calculator">22.5 - 2.5</gadget>
<output>20</output>

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

<gadget id="calculator">120 / 10</gadget>
<output>12</output>

<result>12</result>