Let us use the following number line to find the value

$\left(+6\right)-\left(-9\right)=$

Let us use the following number line to find the value

$\left(-3\right)+\left(-6\right)=$

Let us use the following number line to find the value

$\left(-6\right)+\left(-5\right)=$

Let's verify the following using a number line.

$\left(+2\right)+\left\{\left(+3\right)+\left(+5\right)\right\}=\left\{\left(+2\right)+\left(+3\right)\right\}+\left(+5\right)$

Let's verify the following using a number line.

$\left(-8\right)+\left\{\left(-2\right)+\left(+6\right)\right\}=\left\{\left(-8\right)+\left(-2\right)\right\}+\left(+6\right)$

Let's verify the following using a number line.

$\left(+2\right)-\left\{\left(+3\right)-\left(-5\right)\right\}\ne \left\{\left(+2\right)-\left(+3\right)\right\}-\left(-5\right)$

Let's verify the following using a number line.

$\left(-8\right)-\left\{\left(-2\right)-\left(+6\right)\right\}\ne \left\{\left(-8\right)-\left(-2\right)\right\}-\left(+6\right)$