The ratio of the two numbers of A and B is 2:5, and the number of A is 18 less than the number of B, so what is the number of A?
甲乙两数的比是2：5，甲数比乙数少18，那么甲数是多少．
<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<result>12</result>