operation(s) puzzle

[flamebirde 196]

If

253=243

512=504

854=837

is true, then what does 689 equal?

Hint: = means "do operation(s) and get x as result" where x equals the answer.

EDIT: the answer was random, I assure you.

Edited March 13, 2013 by flamebirde

[googon97 1]

Start with ABC. After the operation it is ABC - A - B - C. In other words, add the digits and subtract it from the original number. Therefore 689 = 666

Edited March 13, 2013 by googon97

[jhawk 3]

I say

The sign of the devil

[nakulendu 2]

the do function "=" is sum up the digits and deduct. So devil's ticket if you please. - 666

[flamebirde 196]

Start with ABC. After the operation it is ABC - A - B - C. In other words, add the digits and subtract it from the original number. Therefore 689 = 666

Nice. Pretty easy, although jhawk technically got it right he didn't explain.