2.45 is smaller.and thats it
The function is discontinuous at x=8 because as x approaches 8 from the left, f(x) approaches -1 but as x approaches 8 from the right, f(x) approaches 1 and -1 and 1 are not equal.
You need to first add up the total cost which is 12.45, then find 6% of 12.45 which is .747 or rounded to.75.(tax) then you need to add it to get 13.20. so the tip was 13.20