The correct question in the attached figure
we know that
to fill the tank is required--------> 100%-20%--------> 80%
if 20% of the gas tank is-----------------> 288.75 gal
80% --------------------------------------> X gal
X=80*288.75/20--------> X=1155 gal
if 1 gal----------------> cost $3
1155 gal----------> $X
X=1155*3--------> X=$3465
the answer is
the cost to fill the tank is $3465
we know that
to fill the tank is required--------> 100%-20%--------> 80%
if 20% of the gas tank is-----------------> 288.75 gal
80% --------------------------------------> X gal
X=80*288.75/20--------> X=1155 gal
if 1 gal----------------> cost $3
1155 gal----------> $X
X=1155*3--------> X=$3465
the answer is
the cost to fill the tank is $3465