Xiao Ding needs to write 42 big characters, and he has already written 24. The rest will take 3 minutes to finish. How many big characters are written per minute on average?
小丁要写42个大字，已经写好了24个，剩下的要3分钟写完，平均每分钟写几个大字？
<gadget id="calculator">42 - 24</gadget>
<output>18</output>

<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<result>6</result>