Given the function f(x) = log2(x + 6), find the value of f−1(3).
f−1(3) = 2
f−1(3) = 3
f−1(3) = 9
f−1(3) = 18
f−1(3) = 2
f−1(3) = 3
f−1(3) = 9
f−1(3) = 18