1.   Alas, it was not nearly so simple, and many more complex problems remained to be solved.

2.   By day, this urbane, well-educated man mastered complex problems in a high-tech consulting firm.

3.   Complex problems can arise where one of the purposes is lawful and one is regarded as unlawful.

4.   Crime is a complex social problem with no single cause or solution.

5.   It is impossible to take a complex problem and rationally unravel the mess into logical interacting pieces.

6.   The search for comprehensive solutions to complex urban problems has once again defied disciplinary and professional boundaries.

7.   The three ravening bolts of fury launching themselves at him now, presented an entirely more complex problem.

8.   The visionary leader is a transformer, cutting through complex problems that leave other strategists stranded.

9.   The Web community of developers and users is tackling these complex problems.

10.   There is no simple solution to this complex problem.