1. The problem states that there are 12 blue triangles for every 27 yellow triangles. 2. We are asked to find the ratio of yellow triangles to blue triangles. 3. The given ratio is blue : yellow = 12 : 27. 4. To find yellow : blue, we take the reciprocal of the given ratio. 5. So, yellow : blue = 27 : 12. 6. Simplify the ratio by dividing both numbers by their greatest common divisor (GCD), which is 3. 7. $$\frac{27}{\cancel{3}} : \frac{12}{\cancel{3}} = 9 : 4$$ 8. Therefore, the ratio of yellow triangles to blue triangles is $9 : 4$.