12-5h=h+6 whats the answer

Pls! does anybody know a shortcut for answering these types of questions in the future?

Aword processing program requires a 7- digit registration code made up of the digits 1,2,4,5,6,7 and 9 each number has to be used and no number can be used mor than once how many codes are possible

Meee i honestly dont know what this question talking about