When we move to the left on the number line the numbers are decreasing, which means we're subtracting. When we move to the right, the numbers are increasing, which means we're adding.
To find 3 units to the left of -15 we just need to subtract 3 units from - 15.
[tex]-15-3=-18[/tex]
3 units to the left of -15 is -18.
To find 2 units to the right of -12 we just need to add 2 units from - 12.
[tex]-12+2=-10[/tex]
The difference between the elements on the number line is 1 unit, and using the first statement, we have that the blanks are
-22 -21 -20 -19 -18 -17 -16
