A person rides a bicycle from A to B. If he travels 10 kilometers per hour, he will arrive at B at 1 p.m. If he travels 15 kilometers per hour, he can reach B at 11 a.m. Now he wants to arrive at B at 12 noon. How many kilometers per hour should the speed be to reach point B?
一个人骑自行车从甲地到乙地，如果每小时行10千米，在下午1时到达乙地，如果每小时行15千米，在上午11时可以到达乙地，现在他希望在中午12时到达乙地，每小时应以多少千米的速度前进．
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<gadget id="calculator">30 / 5</gadget>
<output>6</output>

<gadget id="calculator">10 * 6</gadget>
<output>60</output>

<gadget id="calculator">60 / 5</gadget>
<output>12</output>

<result>12</result>