The tree-lined road in a certain city has been built to the full length (3/10), and another 15 kilometers will be repaired to just half of the full length. How long is this boulevard in kilometers?
某市修建林荫路，已修了全长的(3/10)，再修15千米正好修完全长的一半．这条林荫路全长多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 / (1/5)</gadget>
<output>75</output>

<result>75</result>