Final answer:
The lengths of a square's sides can be found by taking the square root of the area. For the green square with an area of 9 ft², the side length is 3 feet. Similarly, the red square with an area of 16 ft² has a side length of 4 feet, but more information is needed to determine the length of side C.
Step-by-step explanation:
To find the length of side C, we need to know more information about how the sizes of the squares or their relationship to side C are given. However, from the context provided, it seems like two squares with areas of 9 ft² (green square) and 16 ft² (red square) are mentioned. Since the area of a square is given by the formula side², we can find the side length by taking the square root of the area. For the green square, the side length is √9 = 3 feet, and for the red square, √16 = 4 feet. However, without additional context about how side C is related to these squares, we cannot determine the length of side C.