Question

which numbers are four units from -1?

It may help to look at a number line like the following (as an example):


<--- -5 --- -4 --- -3 --- -2 --- -1 --- 0 --- 1 --- 2 --- 3 --- 4 --- 5 --->

Can you determine which numbers (both negative and positive) could be 4 units from -1 ?

I'm not sure if this is what you were asking, but I hope this helps.