Simply create an slope-intercept equation using the given information. The initial fee is $5, which is the y-intercept and $2.75 every stop, which is our slope. The equation is y = 2.75x+5. Since this is an inequality and she's looking for the most amount of stops she can take before maximizing her budget, it needs to be a less than or equal to sign. Change the equation to be 5+2.75S≤21. Subtract 5 from both sides to get 2.75S≤16. Divide 2.75 to both sides to get S≤5.82. This would be estimated to around 5 stops, which would be the largest amount of stops.
