From A to B, the bus travels 20% of the whole journey, and another 30 kilometers will just complete half of the journey. How many miles is it from A to B?
从甲地到乙地，客车行了全程的20%，再行30千米就正好行完了全程的一半．甲地到乙地全程多少千米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">30 / (3/10)</gadget>
<output>100</output>

<result>100</result>