2(5b-7)=-84what is b? and how do i get the answer?

Someone answer this asap for the first five terms of a sequence are shown. 5, 11, 23, 47, 95, . . which recursive function defines the nth term in the sequence for n > 1? a. f(n) = f(n - 1) + 6 b) f(n) = f(n - 1) + 48 c) f(n) = 3 • f(n - 1) + 1 d) f(n) = 3 • f(n - 1) - 4

Me i’m stuck on all these questions besides the two bottom ones

The answer is 7.2 how would you put this as money