If employee a logged 120 hours of travel in four years and employee b logged hours of travel at a 20% higher rate, how many more hours did employee b have than employee a after 1.5 years

Traveled hours by a in four years = 120
Traveled hours by b in four years = (120/100) * 120
                                                      = 144
Excessive hours traveled by b in 4 years           = 144 - 120
                                                                           = 24
Excessive hours traveled by b in 1.5 years        = (24/4) * 1.5
                                                                           = 9 hours