Answer
$809.0$ $mm$ $Hg$
Work Step by Step
Convert from inches of Hg to centimeters of Hg. Then convert from centimeters of Hg to millimeters of Hg.
$31.85$$in$ $Hg$$\times\frac{2.54 cm Hg}{1 in Hg}\times\frac{10 mm Hg}{1 cm Hg}$$=809.0$$in$$Hg$