(29.8)10 convert to binary,octal,hexadecimal?

Digits in hexadecimal are 0 through 9 and letters a through f. Numbers are preceded by '0x'.
Figure the largest hexadecimal number you can subtract from 29.8. That would be 0x10.
Subtract as many times as you can. The number of times is your first hex digit. 0x1-
The remainder is 13.8 decimal. Do the process again. 13 = 0xd. Answer so far is 0x1d.

I never tried to convert decimals, but you do it the same way. It tends to be confusing.