to answer it easily, you should tabulate first the data
Rate(r) Time(t) Distance(d)
Car A 80kph t 528-d
Car B 96kph t d
since we are looking for the time we can equate the equation in terms of the distance(d)
d=rt
For Car A
528-d=(80)(t)
d=-80t + 528
For car B
d=96t
equating both
96t=-80t + 528
176t=528
t=3
therefore, in 3 hours, they would be 528km apart