To determine the number that should replace the letter [tex]\( x \)[/tex] in the "Seed color" row, we proceed as follows:
1. Identify the total number of plants: The total number of plants observed for seed color is given to be 18,066.
2. Determine the number of yellow seeds: It is stated that there are 6,022 yellow seeds.
3. Find the number of green seeds: To find the number of green seeds, subtract the number of yellow seeds from the total number of plants.
[tex]\[
x = 18,066 - 6,022
\][/tex]
4. Calculate the result:
[tex]\[
x = 12,044
\][/tex]
Therefore, the number that should replace the letter [tex]\( x \)[/tex] in the "Seed color" row is 12,044.