Answer
(a) $-1.9$
(b) inverted
(c) $1.2m$
Work Step by Step
(a) We know that
$m=\frac{-d_i}{d_{\circ}}$
We plug in the known values to obtain:
$m=-\frac{3.5m}{1.8m}$
$m=-1.9$
(b) Since the magnification $m\lt 0$, the image formed is inverted.
(c) As $\frac{1}{f}=\frac{1}{d_{\circ}}+\frac{1}{d_i}$
We plug in the known values to obtain:
$\frac{1}{f}=\frac{1}{1.8m}+\frac{1}{3.5m}$
This simplifies to:
$f=1.2m$