A, B, C, D, and E are five different integers arranged from small to large. By adding every two of them together, ten sums can be obtained. Eight of these ten sums are different: 17 respectively. , 22, 25, 28, 31, 33, 36 and 39. Find the average of these five integers.
A、B、C、D、E是从小到大排列的五个不同整数，用其中每两个数相加，可以得到十个和，这十个和中不相同的有八个：分别是17、22、25、28、31、33、36与39．求这五个整数的平均数．
<gadget id="calculator">7 + 10 + 15 + 18 + 21</gadget>
<output>71</output>

<gadget id="calculator">71 / 5</gadget>
<output>71/5 = around 14.2</output>

<result>71/5 = around 14.2</result>