Advanced Work Rate Word Problem
" A man can lay a concrete sidewalk in 5 days; his assistant can lay the same sidewalk in 8 days. After working together for 2 days, the man is called away. How long will it take the assistant to finish the work? "
I am familiar with combined work rate story problems, but I don't quite know how to tackle the one worker leaving the other midway through to finish the job. I've done this problem several different ways and still haven't been able to figure it out.