Let's calculate the areas of all three gardens
First garden
one garden that is 3 feet wide and 3 feet long
Area = length* width = 3 feet * 3 feet = 9 square feet
Second garden
3 feet wide and 6 feet long
Area = 3 feet * 6 feet = 18 square feet
Third garden
3 feet wide and 9 feet long
Area = 3 feet * 9 feet = 27 square feet
It means as we can see as the length increases by 2 times , the area also increases by 2 times every time.