The ratio of A to B is 3:8, the sum of the two numbers of A and B is 33, find the number of A.
甲与乙的比是3：8，甲、乙两数的和是33，求甲数．
<gadget id="calculator">3 + 8</gadget>
<output>11</output>

<gadget id="calculator">33 / 11</gadget>
<output>3</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>