Answer:
Javier can buy at maximum about 3.7 gallons of oil.
Explanation:
Let g represent the amount of gasoline in galloons.
We know that Javier has at most $15.00 to spend. In other words, the total cost after buying the snacks and gasoline must be less than or equal to 15.
He already bought a snack and a drink for a total of $2.59.
And each gallon of gasoline costs $3.39.
So, we can write the following inequality:

To find how many galloons of gasoline Javier can buy, we will need to solve for g.
So, subtract 2.59 from both sides. This yields:

Divide both sides by 3.39:

So, Javier can buy at maximum about 3.7 gallons of oil.
And we're done!