Take 9: x (x>0), expand the latter term of the ratio by 9 times, and how much to increase the former term of the ratio.
把9：x(x＞0)，把比的后项扩大9倍，比的前项增加多少．
<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<gadget id="calculator">81 - 9</gadget>
<output>72</output>

<result>72</result>