ANSWER
15 gallons
EXPLANATION
The equation that models the situation is
[tex]g(m) = 15 - \frac{m}{32} [/tex]
When the tank was full the man did not cover any mile.
To find the the number of gallons of gases Vera's tank holds, we substitute m=0 into the equation to get,
[tex]g(0) = 15 - \frac{0}{32} = 15[/tex]
Therefore the correct answer is is option A 15 gallons