The difference between the real time and the time of the mirror image is two hours and ten minutes
(two and a half hours, minus the twenty minutes of cycling).
Therefore, the original time on the clock at home that morning could only have been five minutes past seven:
The difference between these clocks is exactly 2 hours and ten minutes
(note that five minutes past one can also be mirrored in a similar way, but this is not in the morning!).
Conclusion: The boy reaches school at five minutes past seven plus twenty minutes of cycling,
which is twenty-five minutes past seven!
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