In order to welcome the New Year, the students in the fourth grade are going to make 180 big red flowers to beautify the classroom. They make 42 flowers per hour on average. After 4 hours of making, how many big red flowers do they need to make to complete the task?
四年级的同学为了迎接新年，准备制作180朵大红花来美化教室，他们平均每小时做42朵，做了4小时后，还需要做多少朵大红花才能完成任务？
<gadget id="calculator">42 * 4</gadget>
<output>168</output>

<gadget id="calculator">180 - 168</gadget>
<output>12</output>

<result>12</result>