A list of numbers or diagrams that are in a particular order ... Look at the difference between one pattern and the next in the sequence. Here, 1 yellow circle and 2 red squares are being added ...

One poster @NguyenDung14133 trying to solve the riddle said: "D) 18". another user, @22Willem1, reckoned the answer was 18. Using the differences in the number pattern, you can use you problem ...