This question exercises Visual-Spatial Perception and Systematic Scanning. It challenges the brain to decompose complex patterns into basic units and then reassemble them into larger structures, which is vital for maintaining attention to detail.

The Logic: To avoid missing any, count the triangles based on their size-from the smallest individual pieces to the largest overall frame.

The Calculation: 1. Small Triangles: There are 9 basic small triangles (5 on the bottom, 3 in the middle, and 1 at the top).
2. Medium Triangles: There are 7 medium triangles (each composed of 4 small triangles).
3. Large Triangles: There are 2 large triangles (each composed of 9 small triangles).
Total: 9 + 7 + 2 = 18 triangles.

Stay Sharp Tip: When looking at complex objects like buildings or tiled floors, try to find hidden geometric shapes. This type of "visual searching" keeps your brain's occipital and parietal lobes active, helping you maintain sharp vision and spatial awareness.