The elder brother has 100 yuan, and the younger brother has 80 yuan. After the elder brother gives the younger brother how much money, the ratio of money between the two brothers is 7:11.
哥哥有100元钱，弟弟有80元钱，哥哥给弟弟多少元钱后，兄弟俩的钱数比是7：11．
<gadget id="calculator">100 + 80</gadget>
<output>180</output>

<gadget id="calculator">7 + 11</gadget>
<output>18</output>

<gadget id="calculator">7 / 18</gadget>
<output>7/18 = around 0.388889</output>

<gadget id="calculator">180 * (7/18)</gadget>
<output>70</output>

<gadget id="calculator">100 - 70</gadget>
<output>30</output>

<result>30</result>