First find out the triangle (red) in the top left.
The area of a triangle is found by length times width and divide it all by 2 because a triangle is half of a square. Now we multiply that by 2 for the second triangle (in green) at the bottom. We can do this because the blue does to the half way mark on the quilt so the other triangle on the bottom has to be the same.
Now we find out the area of the whole SQUARE quilt. It already gave the measurement of one side so they all have to be the same.
Now we only need the area of the side the blue is on. So divide by 2 and get 72.
Now subtract 18 from 72.
The answer is 54 for blue.