Let's define
x: time is hours
Coach A services costs 4800 + 550x dollars
Coach B services costs 4500 + 700x dollars
If both coaches charge the same:
4800 + 550x = 4500 + 700x
4500 is adding on the right, then it will subtract on the left
550x is adding on the left, then it will subtract on the right
4800 - 4500 = 700x - 550x
300 = 150x
150 is multiplying on the left, then it will divide on the left
300/150 = x
2 = x
The two coaches will charge the same amount of money after 2 hours.