The ratio of the numbers A and B is 2:3, the number B is 30 more than the number A, what is the number A?
甲乙两数的比是2：3，乙数比甲数多30，甲数是多少．
<gadget id="calculator">3 - 2</gadget>
<output>1</output>

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

<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<result>60</result>