Answer
$\log _b \dfrac {p}{qr}$
Work Step by Step
$\log _{b}p-\log _{b}q-\log _{b}r=\left( \log _{b}p-\log _{b}q\right) -\log _{b}r=\log_b \dfrac {p}{q}-\log _{b}r=\log _b \dfrac {p}{qr}$
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