Question

When it is 2 hours after 2 o'clock, then it is 4 o'clock (2 + 2 = 4). When it is 10 hours after 10 o'clock, then it is 8 o'clock. In this kind of "clock arithmetic," 10 + 10 = 8. When a clock time gets bigger than 12, you subtract 12 and take the answer as the actual clock time. For example, if you subtract 12 from 20, the answer is 8, so 20 o'clock is really 8 o'clock. Brad has a certain medication that he needs to take every 5 hours without fail, starting at 1 o'clock on a certain day. The sequence of clock times that he takes his pills is 1, 6, 11, 4, 9, ... What is the clock time when Brad takes his 16th pill? Enter a number from 1 to 12.

Answer 1

Start with 1 and add on 5 each time
1, 6, 11, 16, 21, etc

The nth term of this pattern is 
an = 1+5(n-1)
so the 16th term is
a16 = 1+5(16-1)
a16 = 76

Divide 76 over 12. Use long division to get 
76/12 = 6 remainder 4

The remainder 4 tells us that it will be 4 o'clock when he takes the 16th pill

Answer: 4 o'clock
Note: I'm not sure if its am or pm, though I don't think your teacher seems to mind either way

Answer 2

It will be 4 o'clock when Brad takes his 16th pill.

Hope it helps