The ratio of the numbers A and B is 6:7, the number B is subtracted from the number A to get 30, what is the number A?
甲、乙两数的比是6：7，乙数减去甲数得30，甲数是多少．
<gadget id="calculator">7 - 6</gadget>
<output>1</output>

<gadget id="calculator">30 / 1</gadget>
<output>30</output>

<gadget id="calculator">30 * 6</gadget>
<output>180</output>

<result>180</result>