1. The problem is to evaluate the expression $2 + [ = -1$. However, the expression appears to have a syntax error or typo with the bracket and equal sign. 2. Assuming the intended expression is $2 + (-1)$, which means adding 2 and -1. 3. The formula for addition of integers is $a + b = c$, where $a$ and $b$ are integers. 4. Applying the formula: $2 + (-1) = 2 - 1 = 1$. 5. Therefore, the value of the expression is $1$.