Answer
$\approx -0.579352$
Work Step by Step
RECALL:
The change-of-base formula for logarithms:
$\log_b{x} = \dfrac{\log_a{x}}{\log_a{b}}$
Use the formula above and use base 10 to obtain:
$\log_9{0.28} = \dfrac{\log{0.28}}{\log{9}}$
Use a scientific calculator and round-off the answer to six decimal places to obtain:
$\approx -0.579352$