I have explained number system in computer working and Binary to decimal , octal to decimal and hexadecimal conversion.
how to convert binary to decimal?
how to convert octal to decimal?
how to convert hexadecimal to decimal ?
all the conversions are explained this video.

Chapters:
0:00 Intro
0:10 Recap
0:33 Binary to Decimal conversion with fraction
1:47 Decimal to Binary conversion with fraction
3:34 Octal to Decimal conversion with fraction
4:28 Decimal to octal conversion with fraction
4:54 Hexadecimal to Decimal conversion
5:21 Decimal to Hexadecimal conversion
5:38 Number System and conversion formula