How do we solve this problem? (oh and ignore the circled answer. i just need to know how to solve this)

To solve the problem you must find the area of every square. For F one of the squares has a side length of 3 and because this is a square the other sides are also 3. To find the area we multiply two of the sides so 3 times 3 is 9
You do this with both the other squares
3*3=9
4*4=16
The area of the large square is given as 25
So 9+16=25 which means this is not the correct answer

H.
9*9=81
Given as 144
The area of the large square is 21*21 which is 441
144+81= 225
So because the two small squares DO NOT equal the area of the large square this is the correct answer.