1. 13 was believed to have been an unlucky number. 
     It was believed that 13 is an unlucky number. 
2. English is known to be an international language. 
     It is known that English is an international language. 
4. John was said to have been the brightest student in the class. 
     It was said that John is the brightest student in the class. 
7. He is thought to have died a natural death. 
    It is thought that he has died a natural death.