There are 4 different natural numbers a, b, c, d and 0<a<b<c<d. If ba=5, dc=7, the average of a, b, c, d is 17, then what is the maximum value of d.
有4个不同的自然数a，b，c，d而且0＜a＜b＜c＜d．如果b-a=5，d-c=7，a，b，c，d的平均数是17，那么d最大是多少．
<gadget id="calculator">28 - 1</gadget>
<output>27</output>

<gadget id="calculator">7 + 27</gadget>
<output>34</output>

<result>34</result>