Hexadecimal number system uses 16 different symbols;0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
So in our case we must first find the largest power of 16 thats smaller than the decimal number 20.
so:
20/16=1.25 so 1 is the first digit of our hexadecimal number.
Next step is to find the remainder.
20-16=4 so 4 is our remainder.
once you get a remainder from 0-15 it can be expressed by a single hexadecimal digit.so 14 is the hexadecimal of the decimal number 20.