I just learned about this!
How to get Number 1: This closed circle represents it is more than or equal to 4. so it should be x ≥ 4.
How to get number 2: This circle is open which means it is NOT equal to or close to the number so it should be x≠-4. Because you don't know how much x is and the lines and arrows represent it is not equal.
Number 3: The first option is the correct one as it says clearly x is less than -3 so it should be a open circle.
Number 4: The 2nd one is right because x is less than -1 or equal to -1.
