He Jun drove from Shunde to Guangzhou for a meeting at a speed of 60 kilometers per hour, and he will arrive 30 minutes earlier. If he travels at a speed of 36 kilometers per hour, he will be half an hour late, so how many hours will he have to start the meeting from when he is driving.
何军自驾车从顺德到广州开会，时速60千米，他将会提前30分钟到达．若以时速36千米前进，会迟到半小时，那么他从开车时算起还有多少小时才开会．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">1 / 36</gadget>
<output>1/36 = around 0.027778</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/36) - (1/60)</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">1 / (1/90) / 60</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(3/2) + (1/2)</gadget>
<output>2</output>

<result>2</result>