Convert these decimal into a fraction 0.457, 0.797, 0.815, and 0.242

The fraction form of theses numbers are just as they sound aloud.

0.457 is four hundred fifty seven thousandths, so we write it as 457/1000

the same goes for the other three numbers

0.797 797/1000

0.815 815/1000

0.242 242/1000

granted 242/1000 can be simplified to 121/500 and 815/1000 can be simplified to 163/200. Though that only matters if you're asked to simplify.