6: Add 9 to the preceding term of 7, how much should 7 be multiplied to keep the ratio unchanged?
6：7的前项加上9，要使这个比的比值不变，7应该乘多少
<gadget id="calculator">6 + 9</gadget>
<output>15</output>

<gadget id="calculator">15 / 6</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>