Think about it, do the math: Uncle Li traveled to Mount Tai by bicycle. He has ridden the whole journey (2/5) from home until now, and he is still 80 kilometers away from the midpoint. How many kilometers does Uncle Li have to travel from his home to Mount Tai?
想一想，算一算：李伯伯骑车去泰山旅游，从家出发骑到现在，行了全程的(2/5)，离中点还有80千米．那李伯伯从家到泰山一共要行多少千米呢？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">80 / (1/10)</gadget>
<output>800</output>

<result>800</result>