18) slope and y-intercept, I need help ASAP

[15 points, algebra 2]simplify the complex fraction and find the restrictions.

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

For the inequality |c| < |d| to be true, which of the following must be true?