Answers:

1. 456_{7} =_{ }237_{ }2. 25_{6} =_{ }17_{ }3. 100_{5} =_{ }25 (Note that in 25 is 5 squared, which was the base, and 100 is 10 squared, which is what base you're converting it to)._{ }4. 1A2_{16} = 418