### Instruction: Convert $222_{10}$ to base $13$.  Use digits A, B, and C if necessary.### Response: To convert a number from base 10 to base 13, I need to repeatedly divide by 13 and write down the remainders until I get zero.
So, let's start with 222 and divide by 13.
I get 17 as the quotient and 1 as the remainder, so I write down 1 as the rightmost digit of the base 13 number.
Next, I take 17 and divide by 13 again.
This time, I get 1 as the quotient and 4 as the remainder, so I write down 4 as the next digit to the left.
Finally, I take 1 and divide by 13 one more time.
I get 0 as the quotient and 1 as the remainder, so I write down 1 as the leftmost digit.
So, the base 13 number is 141, and I don't need to use any letters.