240 represents the amount it takes for each car. it is your slope/x of the equation.
Create an equation for the total costs of driving x miles: 3.50 + 2.50x
since Sasha has $37, the equation would become: 3.50 + 2.50x = $37
subtract 3.50 from both sides: 2.50x = 33.50
divide 2.50 on both sides: x = 13.4
since the problem is asking for the greatest whole number of miles, you have to round down and the answer would be: 13 miles.
