1 14:22:45 + 11:45:30 = 26:08:15
2 14:22:45 += 11:45:30 = 26:08:15
3 11:05:30 - 01:20:40 = 09:44:50
4 11:05:30 -= 01:20:40 = 09:44:50
9 14:22:45 + 7000 seconds = 16:19:25
10 14:22:45 += 7000 seconds = 16:19:25
11 14:22:45 - 7000 seconds = 12:26:05
12 14:22:45 -= 7000 seconds = 12:26:05
13 PASS hour_arithmetic (exit status: 0)