Using the following numbers for your calculations, how much weight will come off your steer axle?
Miles per gallon: 7
Miles travelled: 280
Fuel weighs: 8 pounds per gallon
Percenatage of fuel weight on steer axle: 80%

Number of miles travelled / miles per gallon = gallons of fuel burned off
<=> 280 / 7 = 40 gallons.
40 gallons x 8 pounds per gallons = 320 pounds of total fuel burned off.
We know that 80% of the 320 pounds of fuel weight we'll burn will come off the steer axle:
(80 x 320) / 100 = 256 pounds.