The number $-3$−3 is plotted on the number line below.

Find the value of $-3+8$−3+8.

The number $-6$−6 is plotted on the number line below.

Find the value of $-6+3$−6+3.

The number $-7$−7 is plotted on the number line below.

Find the value of $-7+7$−7+7.

Find the value of $-7+15$−7+15.