Answer:
Y=2/3x-14/3
Step-by-step explanation:
If you subtract the 2 from the y+2 and from the simplified version of 2/3(4), you get the answer above! I hope this helps!
Their daily rate is

miles per day
Using distance-speed-time formula, we can calculate the time

days
They need 21-3=18 more days to finish the trip
The answer to your question above would be: 7z-2/z-7
I would say the answer would be x = 2y