Answer
(a) $7$
(b) $3$
(c) $3$
Work Step by Step
RECALL:
(1) $\log_b{b}=1$
(2) $\log_b{1}=0$
(3) $\log_b{b^x}=x$
(a) Use rule (3) above to obtain:
$\log_3{3^7}=7$
(b) Write 64 as $4^3$, then use rule (3) above to obtain:
$=\log_4{4^3}
\\=3$
(c) Write 125 as $5^3$, then use rule (3) above to obtain:
$=\log_5{5^3}
\\=3$