Shanyang Town built 20 kilometers of roads this year, 5 kilometers more than last year (1/2). How many kilometers were built last year?
杉阳镇今年修公路20千米，比去年的(1/2)还多5千米．去年修公路多少千米？
<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">15 / (1/2)</gadget>
<output>30</output>

<result>30</result>