Answer
$\log_{5}$125 = 3
Work Step by Step
The logarithm formula using variables is: $\log_{B}$A = C
Using the same variables, the spots they would go in the exponential formula is: B$^{C}$ = A
So to write $5^{3}$ = 125 in logarithm form, you first have to look at which number corresponds to which variable in the exponential formula. In this case:
5 corresponds to B
3 corresponds to C and
125 corresponds to A
Knowing which number corresponds to which variable in the exponential formula, you can then plug those into the logarithm formula to get your answer which will be:
$\log_{5}$125 = 3