Let's say the number of days is d (as stated in the question). there are always 24 hours in a day, so the amount of hours in d days has to be 24*d. since you also have the six hours, this can be written as 24*d + 6 = the number of hours in d days and six hours.
4 + (3x) = y (or total amount)
start with 0, then work your way up:
(0, 4)
(1, 7)
(2, 10)
(3, 13)
(4, 16)
etc
hope this helps
& may Joan of Arc bring you good tidings XD