A section of road was built, the full length (1/4) was built in the first week, and the full length (2/7) was repaired in the second week. A total of 15 kilometers was built in two weeks and one week. How many kilometers is the total length of this road?
修一段路，第一周修了全长的(1/4)，第二周修了全长的(2/7)，两周一共修了15千米，这段路全长多少千米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(1/4) + (2/7)</gadget>
<output>15/28 = around 0.535714</output>

<gadget id="calculator">15 / (15/28)</gadget>
<output>28</output>

<result>28</result>