ill try my best to explain: first, he rode 20 minutes to camp. and once there he saw a time 2 hours and 30 minutes later than the time at home. so we need to subtract the 20 minute bike ride from that which gives you a difference of 2 hours and 10 minutes. after that, we need to figure out what time he left the house. so, for it to be a mirror image, it must be reflected over the y-axis. therefore, either accross the 12 o'clock or the 6 o'clock. Looking at the times it is obvious that we will be working at the bottom over the 6 o'clock. Now divide 2 hours and 10 minutes by 2. You now have 2 sets of 65. One for the mirror image and one for the real time. By adding that 65 to the base at 6 o'clock you get the time that he left. 7:05. And by adding his 20 minute bike ride in you get the time he arrived at school. 7:25. And then by adding 65 to the other side of the clock you can also see what time he saw in the mirror. 4:55. Hope I explained it well enough. Cheers EDIT: Final that's an old one A Stamp