Equations of addition are given. Find the solutions using the number lines.
A. $-7+2$ B. $1+\left( -5 \right)$ C. $-9+5$ D. $8+\left( -3 \right)$

Hint: All the addition we use the number line. We use the concept of positive and negative numbers. We use the direction in which positive and negative numbers go. In the end, we get the ending point of the number line. It becomes the solution to the addition.

Complete step-by-step solution:
We use the number line in all four cases. Every sum has 2 parts. We start from the origin i.e. $\left( 0,0 \right)$.
If the number is positive then we go to the right of the origin and if the number is negative, we go left.
The end position is the solution of the addition.
So, for $-7+2$, we first go left then right.

The final point is -5 which means $-7+2=-5$.
For $1+\left( -5 \right)$ we first go right then left.

The final point is -4 which means $1+\left( -5 \right)=-4$.
for $-9+5$ we first go left then right.

The final point is -4 which means $-9+5=-4$.
for $8+\left( -3 \right)$ we first go right then left.

The final point is 5 which means $8+\left( -3 \right)=5$.

Note: We need to be careful about the numbers we are adding. We only doing addition. This means we need to care about only the signs of it which is positive or negative. That determines the direction of the end solution. Also, it defines the signs of the answer.