It is the third number line.
b-11=-8
What minus 11 would equal -8? 3!
8+3=11 so it would make sense that the dot would be on 3.
smaller numbers minus larger numbers (such as this equation) always end up being negative, so if you have the answer and at least one of the other numbers, it will be easy to figure out.
In this case you would want to maybe just imagine 11-8=? or go 8+?=11.
11-8=3 and 8+3=11. There you would have your missing number.
