Explanation:
The diagram is very helpful, so really go off of that. Coordinates are written in the form (x,y). If you look at the signs (either there's a negative sign, - , or no sign at all, meaning it's +) for each number in a coordinate pair, you can see where each coordinate should go.
If you look at the last example (3, -3), the first digit is positive + and the second digit is negative - . When you look at the diagram, coordinates in the form of (+, -) are put in quadrant 4.