The original number of senior high school students in Huaxing Middle School was junior high school students (7/12). This semester, 30 students were transferred to high school. Now the ratio of the number of senior high school students to the number of junior high school students is 4:9. How many junior high school students are there?
华兴中学原来高中生人数是初中生的(7/12)，本学期高中转走30人，现在高中生人数与初中生人数比是4：9，初中生有多少人？
<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">(7/12) - (4/9)</gadget>
<output>5/36 = around 0.138889</output>

<gadget id="calculator">30 / (5/36)</gadget>
<output>216</output>

<result>216</result>