I believe you are referring to exponents that have a multiple of three. If so any number * three is a valid exponent in your case.
the original cost was $111.60.
I thonk it s 6 miles not sure though :-)
Here is the equation you need:
3(x + 9) = 2x - 7
You finish.
Answer:
3
Step-by-step explanation:
It's decreasing by 3 each time, so the next number in the sequence would be 6 - 3, which is 3.