Answer
$d_o=64.7cm$
$d_o=21.3cm$
Work Step by Step
$d_i+d_o=86cm$
$d_i=\frac{1}{\frac{1}{f}-\frac{1}{d_o}}=\frac{1}{\frac{1}{16.0cm}-\frac{1}{86cm-d_i}}=\frac{1376-16d_i}{70cm-d_i}$
$70d_i-d_i^2=1376-16d_i$
$d_i^2-86d_i+1376=0$
$d_i=21.3cm$
$d_i=64.7cm$
$d_o=64.7cm$
$d_o=21.3cm$
