To build a highway, the length ratio between the completed and unbuilt is 1:3, and then build another 30 kilometers, the one that has been built will be the one that has not been built (1/2), how many kilometers is this highway?
修一条高速公路，已修和未修的长度比是1：3，再修30千米，已修的就是未修的(1/2)，这条高速公路长多少千米？
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/3) - (1/4)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">30 / (1/12)</gadget>
<output>360</output>

<result>360</result>