Answer
$3-\log_5{y}$
Work Step by Step
RECALL:
The quotient rule for logarithms states:
$\log_a(\frac{b}{c})=\log_a{b}−\log_a{c}$
Use the quotient rule to obtain:
$=\log_5(125)-\log_5{y}
\\=\log_5{(5^3)}-\log_5{y}$
Note that for all real numbers within its domain, $\log_a{(a^n)}=n$.
This means that $\log_5{(5^3)}=3$.
Thus,
$\log_5{(5^3)}-\log_5{y}=3-\log_5{y}$