Answer :
900/1200 can be simplified down to 3/4, so 1/4 of the trip is still needing to be completed
900 miles of 1200 miles means: 900/1200.Those numbers are divisible to 3. The 300/400, the zeros have been taken away. So, you've got 3/4. You know that the difference between 4/4-3/4 =1/4. So, 1/4 is your percentage.