Simple Subtraction E782Af

1. The problem is to calculate the value of the expression $1-2$. 2. The formula used here is simple subtraction: $$a - b$$ where $a=1$ and $b=2$. 3. Subtract $2$ from $1$: $$1 - 2$$. 4. Since $2$ is greater than $1$, the result will be negative. 5. Perform the subtraction: $$1 - 2 = -1$$. 6. Therefore, the final answer is $-1$.