If you would like to know how many miles does Brian need to drive each hour, you can calculate this using the following steps:
324 miles ... 6 hours
x miles = ? ... 1 hour
324 * 1 = 6 * x
324 = 6 * x /6
x = 324 / 6
x = 54 miles
Result: Brian needs to drive 54 miles each hour.