The ratios of the side lengths are:
3:5
4:7
6:2
The ratio of the area of a figure is the square of the ratio of the sides. To find the ratio of the sides from the ratio of the area, we take the square root of each one:
√9:√25 = 3:5
√16:√49 = 4:7
√36:√4 = 6:2