1.We found that they were clever enough to learn English well.= We thought they were clever enough to learn English well.
2.Lesson Nine is the most difficult one in Book 2= The most difficult lesson in Book 2 is lesson nine.
3.He used a lot of money to buy things for his lab= He spent a lot of money to buy things for his lab.
4.he ran as fast as he could to catch the thief= He did his best to catch the thief.
5.all the student passed the exam but bill didn't=All the student passed the exam except Bill.