85 mi on 9 gallons of fuel is 85/9 mi per gallon=9 4/9= 9.44mi per gallon; or 1 mile on 9/85=0.11 of a gallon.
13 in of snow in 4 hrs is 13/4=3.25 in per hour; or 1 in of snow in 4/13hr or 4/13*60 minutes=240/13=18.46 mins.
$6 for 4 cans of tuna is 1 can (unit) costing $6/4=$3/2=$1.50 per can or $1.50 a unit.