To build a road, the full length (2/7) has already been built. If another 30 meters are built, the ratio of the already built to the full length is 1:2. How many meters is the total length of this road?
修一条路，已修全长的(2/7)，若再修30米，这时已修与全长的比是1：2，这条路全长多少米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/2) - (2/7)</gadget>
<output>3/14 = around 0.214286</output>

<gadget id="calculator">30 / (3/14)</gadget>
<output>140</output>

<result>140</result>