Answer
0.493008
Work Step by Step
$Use$ $the$ $Change$ $of$ $Base$ $Formula$ $and$ $a$ $calculator$ $to$ $evaluate$ $the$ $logarithm$:
$\log_7 2.61$
Apply the Change of Base Formula: $\log_x y$ = $\frac{\log y}{\log x}$
$\log_7 2.61$ = $\frac{\log 2.61}{\log 7}$
Use a calculator and round to the sixth decimal place
$\approx$0.493008