Answer:
To solve this problem, we need to take the following steps:
Step 1: Notice that the pattern of the numbers is decreasing by 11 each step.
Step 2: To find the value of n, subtract 11 from 51 to get 40.
Step 3: Subtract 11 from 40 to get 31.
Step 4: Subtract 11 from 31 to get 20.
Step 5: Subtract 11 from 20 to get 9.
Therefore, the answer for n is 9.