There are 76 pieces of a product, sold to 33 customers, each customer can buy up to 3 pieces, buy one at the original price, buy two pieces at a 10% price reduction, buy three pieces at a 20% price reduction, and finally settle the average price of each piece exactly at the original price 85% are sold, so how many customers buy three pieces?
某商品有76件，出售给33位顾客，每位顾客最多买3件，买一件按原定价，买两件降价10%，买三件降价20%，最后结算平均每件恰好按原价的85%出售，那么买三件的顾客有多少人？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">43 * (4/5)</gadget>
<output>172/5 = around 34.4</output>

<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">76 * (17/20)</gadget>
<output>323/5 = around 64.6</output>

<gadget id="calculator">33 * 1</gadget>
<output>33</output>

<gadget id="calculator">(323/5) - 33</gadget>
<output>158/5 = around 31.6</output>

<gadget id="calculator">(172/5) - (158/5)</gadget>
<output>14/5 = around 2.8</output>

<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(4/5) - (3/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(14/5) / (1/5)</gadget>
<output>14</output>

<result>14</result>