We are given pattern 615,605,595.
Let us check differences of second term - first term and
Third term - second term
Second term - first term = 605 - 615 = -10.
Third term - second term = 595 - 605 = -10.
So, each time 10 is being subtracted from previous term.
So, the sequnace would be
615, 605, 595, 585, 575, 565.