If f (x) = log2 (x + 4), what is f-1 (3) ?

T = log2 (x+4)

2^t = x+4

x = 2^t - 4

So the goal is to set f (x) equal to new variable and express x depending on that variable. that is what f-1 (x) means

to find f-1 (3) we have to express 3 in our new function f (t)

f (t) = 2^3 - 4 = 4