Final answer:
Wilson has 60% of the bookcase left to paint and will need 30 more minutes to finish painting the entire bookcase based on the established rate.
Step-by-step explanation:
Wilson paints 40% of a bookcase in 20 minutes. To figure out how much more time it will take him to finish the bookcase, we need to understand that he has 60% of the bookcase left to paint. Since 40% corresponds to 20 minutes, we can find out the time needed for 100% by setting up a proportion where 40% is to 20 minutes as 100% is to x minutes. Solving the proportion, x = (20 minutes / 40%) * 100% = 50 minutes.
Now, since Wilson already spent 20 minutes on the first 40%, he has 50 minutes - 20 minutes = 30 minutes left to paint the remaining 60%. Thus, the answer is 30 minutes.