Answer:
-6
Explanation:
The blue point would be at -6 because we can see that each tic mark represents 3 based on the numbers by the other marks 3 to 0 is 3 and 0 to -3 is 3 therefore the next one would be 3 away and 3 from -3 is -6
I hope this helps and please don't hesitate to ask if there is anything still unclear!