To find the missing pattern, we need to analyze the given sequences and identify any consistent patterns or systems of logic in the arrangements. Let's examine the details in each of the triangles:

1. First Triangle:
   • The numbers 21, 7, 4, and 20 seem to be positioned at the vertices. Analyzing letter-position pairs:
     • A = 1: Letter A is at position 1 in the alphabet. Here denoted at the bottom left.
     • X at the center: No direct relation apparent, but might indicate a placeholder or balancing point.
2. Second Triangle:
   • The numbers U, G, A, D, T can be converted to their respective alphabetical positions (U=21, G=7, A=1, D=4, T=20).
   • We can observe that the numbers on the edges equal the alphabetical position of these letters.
3. Fourth Triangle:
   • The numbers O=15, E=5, B=2, H=8 relate to one another using letters to numerical order.

From these observations, we infer the rules:

• Each triangle consists of alphabets at edges and central points, which act similarly across triangles.
• The numerical translation of letters is consistent (letter position in the alphabet).
• Central letters such as X, Z might represent placeholders or hidden logic impacts.

A potential structure of the missing triangle would follow:

• Apply consistent alphabetical conversion to numbers. If something follows 15-5-2-8, then likely numerical order needs derivation or verification.

After analyzing options, the correct solution can be detected based on offered design choices for continuity:

The chosen pattern successfully follows via alphabetic place conversion, utilizing number positioning, and aligning logically with other visible patterns. Therefore, option with image identified is correct.