An express bus travels 320 miles in the same amount of time that a car travels 280 miles. the rate of the car is 8 mph less than the rate of the bus. find the rate of the bus.

Form 2 equations

distance = rate * time

for the bus:-
320 = rt                  where r is the rate of the bus
For the car 
280 = (r - 8)t

from first equation:-   t = 320/r

so substituting in secod equation:-

280 = 320(r - 8)/ r
280r = 320r - 2560
40r = 2560
r = 2560/40 =   64

rate of bus = 64 mph