In a workshop, the ratio of male to female workers is 5:7. Later, 20 male workers were transferred in. At that time, the ratio of male to female workers was 7:9. How many male workers are there in this workshop?
一个车间，男女职工比是5：7，后来又调进男职工20人，这时男女职工的人数比是7：9，这个车间现有男职工多少人？
<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(7/9) - (5/7)</gadget>
<output>4/63 = around 0.063492</output>

<gadget id="calculator">20 / (4/63)</gadget>
<output>315</output>

<gadget id="calculator">315 * (7/9)</gadget>
<output>245</output>

<result>245</result>