1. The problem is to simplify the expression $2_2$. 2. The notation $2_2$ typically means the number 2 in base 2. 3. In base 2, the digit 2 is invalid because base 2 only allows digits 0 and 1. 4. Therefore, $2_2$ is not a valid number in base 2. 5. If the user meant something else, please clarify the problem.