Correct option is B
Given:
Raju is thrice as good a workman as Ravi.
Raju takes 20 days less than Ravi to complete the work.
Solution:
Let x be the time (in days) taken by Ravi to complete the work.
Since, Raju is thrice as good as Ravi,
Raju takes days to complete the work
According to the problem;
Thus, the time taken by Ravi to complete the work is 30 days.