1. The problem is to find the sum of $-1 + (-2)$. 2. When adding negative numbers, you move to the left on the number line because negative means going in the negative direction. 3. Start at $-1$ on the number line. 4. Then move 2 units to the left (because you are adding $-2$). 5. Moving 2 units left from $-1$ lands you at $-3$. 6. So, $-1 + (-2) = -3$. Complete the sentence: Start at $-1$. Then move 2 in the left direction.