There are only (4/7) seats in the cabin of an airplane with passengers. If there are 12 more passengers, the ratio of occupied seats to empty seats is 9:5. How many passenger seats are there in this airplane?
一架飞机的机舱只有(4/7)的座位坐了乘客，如果乘客再增加12人，则已坐的座位和空座位的比是9：5，这架飞机共有多少个乘客座位？
<gadget id="calculator">9 + 5</gadget>
<output>14</output>

<gadget id="calculator">9 / 14</gadget>
<output>9/14 = around 0.642857</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(9/14) - (4/7)</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">12 / (1/14)</gadget>
<output>168</output>

<result>168</result>