Let's multiply each of the four squares, one by one.
In blue, we see the dimensions are x by x. x times x = x^2
In pink, we see the dimensions are 9 by x. x times 9 = 9x
In green, the dimensions are x by 3. 3 times x = 3x
And finally, yellow's dimensions are 3 by 9. 3 times 9 = 27
We can now just add all these areas to find the total area:
x^2 + 12x + 27
