Two people, A and B, are traveling in the same direction from A and B respectively. A catches up with B at a distance of 9 kilometers from B. If A's speed is doubled, he will catch up with B at a distance of 2 kilometers from B. , what is the distance between A and B in kilometers?
甲乙两人分别从A、B两地同时同向而行，甲在距B地9千米处追上乙，如果甲的速度提高一倍，则在距B地2千米的地方追上乙，则A、B两地相距多少千米．
<gadget id="calculator">9 / 1</gadget>
<output>9</output>

<gadget id="calculator">2 / 1</gadget>
<output>2</output>

<gadget id="calculator">9 - 2</gadget>
<output>7</output>

<gadget id="calculator">9 / 1 / 2 / 1</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) - 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">7 / (5/2) / 2 / 1</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">(7/5) * 9</gadget>
<output>63/5 = around 12.6</output>

<gadget id="calculator">(63/5) - 9</gadget>
<output>18/5 = around 3.6</output>

<result>18/5 = around 3.6</result>