The ratio of A and B is 7:9. When A increases by 63 to keep the ratio unchanged, how much should B be increased?
甲乙两数的比是7：9，当甲数增加63后要使比值不变，乙数要增加多少．
<gadget id="calculator">9 * 10</gadget>
<output>90</output>

<gadget id="calculator">90 - 9</gadget>
<output>81</output>

<result>81</result>