The number of A is the number of B (5/7). The average of the two numbers of A and B is 36. What is the number of A?
甲数是乙数的(5/7)，甲乙两数的平均数是36，甲数是多少．
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">36 * 2</gadget>
<output>72</output>

<gadget id="calculator">1 + (5/7)</gadget>
<output>12/7 = around 1.714286</output>

<gadget id="calculator">72 / (12/7)</gadget>
<output>42</output>

<gadget id="calculator">(5/7) * 42</gadget>
<output>30</output>

<result>30</result>