A complex problem solving process includes
Defining the problem
Inventorying what information is already known or needs to be acquired
Working on the problem
Communicating their answer and how they reasoned about it
Giving a bunch of similar problems is not the student thinking but rather practicing following steps. Instead of a page of similar problems, try giving students fewer problems that are dissimilar or exceptions. Analyze, contrast, explain, dissect… focusing more on demonstrating thinking rather than following steps.