1.   And harder problems require more neurons.

2.   Aggressive driving is a harder problem to solve than behavioral problems like drunken driving or failing to buckle up, he said.

3.   Indeed, Republicans often suggest that Congress should be satisfied with them and leave the harder problems for later.

4.   Instead, Gregory did the harder problems on the last page.

5.   Plutonium is the harder problem.

6.   Seselj was a harder problem.

7.   That is a harder problem to correct.

8.   The industry is also tackling harder problems.

9.   There are other problems even harder to solve.

10.   Blood flow increased more than twice as much in whites as the stress was increased by giving the test subjects harder problems.