The number of girls in the classroom accounted for (1/3) of the total number of students. Later, 9 girls came in. At this time, the number of girls accounted for (2/3) of the total number of students. How many students were there in the classroom?
教室里女生人数占总人数的(1/3)，后来又进来9名女生，这时女生人数占总人数的(2/3)，教室里原有学生多少人？
<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">2 / 1</gadget>
<output>2</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 - (1/2)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">9 / (3/2)</gadget>
<output>6</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">6 / (2/3)</gadget>
<output>9</output>

<result>9</result>