Final answer:
The independent quantity in the problem is the side length of the square, while the dependent quantity is the area of the square, which depends on the square of the side length.
Step-by-step explanation:
Angela is observing the relationship between the area of a square and the side length of each square. In this problem situation, the independent quantity is the side length of the square because it is the variable that can be changed freely. The dependent quantity is the area of the square since it depends on the value of the side length. To elaborate, as the side length increases or decreases, the area will correspondingly increase or decrease based on the square of the side length. The area (A) can be calculated by the formula A = side length².