The difference between the two numbers of A and B is 15. If the decimal point of A is moved to the right, it is exactly equal to 7 times the number of B. What is the number of B?
甲乙两数的差是15，如果甲的小数点向右移一位，正好等于乙数的7倍，乙数是多少．
<gadget id="calculator">10 / 7</gadget>
<output>10/7 = around 1.428571</output>

<gadget id="calculator">(10/7) - 1</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">15 / (3/7)</gadget>
<output>35</output>

<gadget id="calculator">35 * (10/7)</gadget>
<output>50</output>

<result>50</result>