2012 AMC 10B Problems/Problem 19
The easiest way to find the area would be to find the area of 
and subtract the areas of 
and 
You can easily get the area of because you know 
and 
, so 's area is 
. However, for triangle 
you don't know 
However, you can note that triangle 
is similar to triangle 
through AA. You see that 
So, You can do 
for 
and 
Now, you can find the area of which is 
Now, you do 
which turns out to be 
which makes the answer (C).
