24. If you said 12 for January 2nd, February 2nd, etc that’s close, but you forgot about January 22nd, February 22nd and so on. If you are a math whiz and didn’t need a calculator to perform 60 x 60 x 24 x 365, then 31,536,000 works too. If you used 365.25 to account for leap year, then you are a human calculator, but even that’s not entirely accurate due to the leap second. And even accounting for that, it’s only an approximation that there are 365.2422 days in a year.

February, because there are fewer days.

87 is the common answer to this, but it has to be flipped upside down, so I consider L8 more correct.

If you flip the numbers horizontally by 180 degrees:

86 87 88 89 90 91

You see that the blank spot is 87, counting from 86 to 91. However, you need to flip it around, so it becomes L8.

The delivery truck arrived back 20 minutes early, so it would have taken 20 minutes to go from where it met the bicycle to get to the airport and back. Therefore, the bicycle and truck met when the truck was 10 minutes from the airport. Adding those 10 minutes to the 30 minutes the truck had already driven to meet the bicycle means the plane arrived 40 minutes ahead of schedule.