The designer of "Xia Yu" clothing factory has improved the design process. It is calculated that 18 sets of adult clothes can be made with 84 meters of cloth, and each set uses 3 meters of cloth, and the remaining cloth can be used to make 15 sets of children's clothes. How many meters of cloth is used for each set of children's clothes? (Please list the comprehensive formula)
"夏雨"服装厂的设计师改进了设计工艺．经计算用84米布可以做18套成人服装，每套用布3米，剩下的布则正好做15套儿童服装，每套儿童服装用布多少米？(请列出综合算式)
<gadget id="calculator">18 * 3</gadget>
<output>54</output>

<gadget id="calculator">84 - 54</gadget>
<output>30</output>

<gadget id="calculator">30 / 15</gadget>
<output>2</output>

<result>2</result>