1. The problem is to evaluate the expression $23 - 24$. 2. The subtraction operation means we take 24 away from 23. 3. Since 24 is greater than 23, the result will be negative. 4. Calculate the difference: $$24 - 23 = 1$$ 5. Therefore, $$23 - 24 = -1$$. The final answer is $-1$.