Li Ling and Zhang Hua did a total of 319 questions in 5 hours, and Li Ling did a total of 169 questions. How many questions does Zhang Hua do on average per hour?
李玲和张华5小时共做了319道题，李玲一共做了169道题．张华平均每小时做了多少道题？
<gadget id="calculator">319 - 169</gadget>
<output>150</output>

<gadget id="calculator">150 / 5</gadget>
<output>30</output>

<result>30</result>