求解这道题目---**Extracted Content:** **Question Stem:** 13. 君君开始做作业，从镜子里看到钟面 (该钟面只有刻度没有数字) 是 6:15, 做完作业后，再看墙上钟表，钟面上的时刻正好也是 6:15, 他做作业用了 ( )分钟。△ **Translation of Question Stem:** 13. Junjun started doing homework. He saw the clock face in the mirror (this clock face only has markings, no numbers) as 6:15. After finishing homework, he looked at the wall clock again, and the time on the clock face was also exactly 6:15. How many minutes did he spend doing homework? ( ) minutes. △ **Other Relevant Text:** * The phrase "(该钟面只有刻度没有数字)" provides a specific characteristic of the clock face. * The blank parenthesis "( )" indicates where the numerical answer for the duration in minutes should be filled. * The symbol "△" is present next to the blank parenthesis, possibly a handwritten mark. **Chart/Diagram Description:** * **Type:** Analog clock face diagram. * **Main Elements:** * **Shape:** A circular outline representing a clock face. * **Markings:** The circumference of the clock face is marked with small tick marks, which represent minute and hour divisions, typical of an analog clock. No numerical labels (like 1-12) are present on the clock face itself, consistent with the description in the problem stem. * **Hands:** Two hands originate from the center of the clock: * A shorter hand (typically the hour hand) is pointing towards the 3 o'clock position (right side of the clock). * A longer hand (typically the minute hand) is pointing directly downwards, towards the 6 o'clock position. * **Time Shown:** Based on the positions of the hands, the diagram visually represents the time 3:30.