We are to calculate the value of the numbers in base 3. One of the ways to do that is to first convert each number to base 10. Do the arithmetic, then convert back to base 3.
121 base 3 +2122 base 3 - 1200 base 3 - 2111 base 3
Let's convert to base10
See attachment for details
From the workings,
121 base 3 + 2122 base 3 - 1200 base 3 - 2111 base 3 = -221 base 3