Can someone please answer this question please answer it correctly and please show work please help me I need it

Answer:
The blue dot is on -19
Step-by-step explanation:
Each line on the number line is 3 apart.
<--|---|-----|----|----|----|---|---|--|---|---|-->
-21 -19 -16 -13 -10 -7 -4 1 4 7 10
If this answer is correct, please make me Brainliest!