Answer
$\approx -0.654$
Work Step by Step
$= \log_7 (0.28)$
Since the base of the $\log$ function is not $10$, then the change of base formula is required before evaluating by calculator:
$= \frac{\log 0.28}{\log 7}$
by GDC / calculator
$= -0.65417...$
$\approx -0.654$
