The garden is a square. I assume you know how to find the area of a square?.
What if they gave you a constant instead of x+7y and asked to find the area?. Could you do that?.
Suppose they said the garden was square and had side length 15 feet, find the area. Easy enough, 15*15=225.
Well, you do the same thing here. x and y are numbers. They could be anything. Suppose x=1 and y=2. We get 15.
So, if the side length is x+7y, then the area is \(\displaystyle (x+7y)^{2}\).
Now, how do you double x+7y?. When you double something, what do you multiply it by?.
What is half of x+7y?. When you halve something, what do you multiply it by?.
Double or halve x+7y, then square it to find the area. Compare this to \(\displaystyle (x+7y)^{2}\).
Suppose the side length was tripled. Then, we have \(\displaystyle 3(x+7y)\). The area would be \(\displaystyle (3(x+7y))^{2}=9(x+7y)^{3}\)
How does this compare to x+7y?. \(\displaystyle \frac{9(x+7y)^{3}}{x+7y}=9(x+7y)^{2}\). 9 times bigger than before.
So, if we choose x=1 and y=2 as before, then the area goes from 225 square feet to 2025 square feet if the side length is tripled.
This means if we triple the side length, the area is 9 times greater than before.
Get the idea now?.
That's all they're asking for.
