Well since the yellow is equilateral inside another equilateral, we can confirm that logically all three blue triangles are congruent.
The orange triangle and the red triangle are similar.
Using one of the properties of similar triangles, we know that the ratio of the side length of the orange triangle to the side length of the red triangle is 2:3
Because: (2/3)^2 = 4/9 = 20/45
Now we found the ratio and that the blue triangles are congruent, we know that the side length of the orange triangle to the side length of the blue triangle is 2: (2 + 3) = 2:5
That means the AREA must be (according to one of the similarity properties) 4:25
So we calculate the area of the blue triangle and find its 125. ( we also can find it using the red triangle.)
Help! Im stuck too! I got the blue triangle as 125, can someone work off from here?