A steel pipe is 18 meters long. (3/4) is used up for the first time, and (1/2) meter is used up for the second time. How many meters is left in this steel pipe?
一根钢管长18米，第一次用去(3/4)，第二次又用去(1/2)米，这根钢管还剩多少米？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">18 * (3/4)</gadget>
<output>27/2 = around 13.5</output>

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

<gadget id="calculator">18 - (27/2) - (1/2)</gadget>
<output>4</output>

<result>4</result>