0123456789ABCDEF

hexadecimal has sixteen numerals. Therefore, its place value system, rather than being like this: . . .10^2 10^, 10^0 . 10^-1 10^-2 . . . which is the decimal system we all learned in fifth grade, it looks like this . . . 16^2 16^1 16^0 . 16^-1 16^-2 . . . by 10^[number], I mean "ten to the [number] power" or ten times ten until you're timesing as many tens as you have [number]

So if you had the number 111, that would be one plus ten plus one hundred in decimal (base 10), but in hex it would be 1*16^0 plus 1*16^1 plus 1*16^2 Sixteen to the zeroth power is by definition 1, so you have one, plus sixteen, plus 256, so if you were to convert that to decimal, it would be 273