Represents 10 types of digits from 0 to 9, so the base of the number system is 10. This is the most familiar number system with everyone. Similar to other number system, value of digit depends upon the position occupied in the number.
Decimal to binary conversion
Steps:
Example:
Convert (38.625)10 into binary
(38.625)10 = (100110.101)2
Decimal to octal conversion
Steps:
Example:
Convert (180.6875)10 to octal
(180.6875)10 = (264.54)8
Decimal to hexadecimal conversion
Steps:
Example:
Convert (90.675)10 to hexadecimal
(90.675)10 = (5F.A)16
+I don't think you need a tip on decimal number system, as you know it.