The 6 numbers are expressed as a, b, c, d, e, f respectively; the average value of a, b, c, d is 10; the average value of b, c, d, e, f is 14. If f is twice a, then what is the average of a and e?
6个数分别表示为a、b、c、d、e、f；其中a、b、c、d的平均值为10；b，c，d，e，f的平均值为14．若f是a的两倍，那么，a和e的平均值等于多少．
<gadget id="calculator">5 * 14</gadget>
<output>70</output>

<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">70 - 40</gadget>
<output>30</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<result>15</result>