Pedro is traveling on a toll road. He plans to exit the road 5 miles ahead at First Avenue and pay $1.75. He changes his plans and travels 9 miles to Butler Street and pays $2.75.

This problem forces us to assume that Pedro has just entered the toll road. He has gone no miles on the toll road yet.

x, miles traveled on the toll road
y, the toll to be paid for x miles

According to his plan, (5, 1.75), an (x,y) point.
According to what happened, (9, 2.75), another point.

Slope m:
%282.75-1.75%29%2F4

m=1%2F4

Picking the "plan" point and found slope
and putting into point-slope equation form:
y-1%263%2F4=%281%2F4%29%28x-5%29

Simplify and put into slope-intercept form:
highlight%28y=x%2F4%2B1%2F2%29

highlight%28y=x%2F4%2Bhighlight_green%281%2F2%29%29
The y-intercept is 1%2F2.