A convenience store sells mineral water, purchases 4 bottles for 5 yuan, sells 3 bottles for 5 yuan, and makes a profit of 300 yuan, then how many bottles need to be sold.
某便民点销售矿泉水，进货，5元钱4瓶，售出时，5元钱3瓶，要获利300元，那么需售多少瓶．
<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(5/3) - (5/4)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">300 / (5/12)</gadget>
<output>720</output>

<result>720</result>