You would first put the question into an equation.
Miles would equal to gallons.
198=11a
You will simplify it to 1a and to get that you divide both sides by 11.
That would get 18=1a or 18=a
You would then multiply both sides then by 6 on both sides to see if 6 gallons would actually be the same as 138 miles.
Mulitply 6 and 18 and you get 108 which is different from 138 and would not be correct. They do not equal the same and so the answer would be no.