The school held a verbal arithmetic competition. Zhang Ming did 30 questions every minute and completed it in 6 minutes. When Zhang Ming completes the task, Li Hong still needs 4 minutes to complete the task. How many questions does Li Hong do on average per minute?
学校举行口算比赛，张明每分钟做30题，6分钟完成．张明完成任务时，李红还需4分钟才能完成任务．李红平均每分钟做几题？
<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">6 / 10</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">30 * (3/5)</gadget>
<output>18</output>

<result>18</result>