Step-by-step explanation:
If I have a square with sides of 2m, it has an area of 4m^2.
If I have a square with sides of 3m, it has an area of 9m^2.
You might divide 4 by 9 to get the ratio of areas.
A more "mathematical" approach is look at the equation for the area of a square...
where a is the length of the side of the square.
I could setup a ratio of the area of two squares as...