The ratio of A and B is 3:5. It is known that A is 30 less than B, so what is A's number?
甲、乙两个数的比是3：5，已知甲比乙少30，那么甲数是多少．
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<result>45</result>