Selling 6 of a certain commodity at a price of 7 yuan each makes as much profit as selling 4 at a price of 8 yuan. How much is the purchase price of this commodity.
某商品按每个7元的价格卖出6个的利润，与按每个8元的价格卖出4个的利润一样多．这种商品的进货价是每个多少元．
<gadget id="calculator">7 * 6</gadget>
<output>42</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">42 - 32</gadget>
<output>10</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<result>5</result>