Xiao Ming and Xiao Hua are 6 kilometers apart, Xiao Ming is in front and Xiao Hua is behind. The two set off at the same time, heading in the same direction. It is known that Xiao Hua travels 8 kilometers per hour, and Xiao Ming travels 5 kilometers per hour. How many hours does it take for Xiao Hua to catch up with Xiao Ming?
小明、小华两人相距6千米，小明在前，小华在后．两人同时出发，朝同一方向行进．已知小华每小时行8千米，小明每小时行5千米，经过几个小时小华追上小明？
<gadget id="calculator">8 - 5</gadget>
<output>3</output>

<gadget id="calculator">6 / 3</gadget>
<output>2</output>

<result>2</result>