Master Zhang packed a batch of bottled mineral water into a box. When he filled 15 boxes, he found that the number of packed mineral water bottles was 12 bottles less than the number (4/7) of this batch of mineral water bottles. Then he filled another 13 boxes. , just finished. How many bottles of this batch of mineral water are there?
张师傅将一批瓶装矿泉水装箱，当他装满15箱时，发现已装的矿泉水瓶数比这批矿泉水瓶数的(4/7)还少12瓶，接着他又装满13箱，正好装完．这批矿泉水共有多少瓶．
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">15 + 13</gadget>
<output>28</output>

<gadget id="calculator">15 / 28</gadget>
<output>15/28 = around 0.535714</output>

<gadget id="calculator">(4/7) - (15/28)</gadget>
<output>1/28 = around 0.035714</output>

<gadget id="calculator">12 / (1/28)</gadget>
<output>336</output>

<result>336</result>