Jason drives 60 miles per hour * 0.5 hours = <<60*0.5=30>>30 miles initially
He needs to drive an additional 120 miles total - 30 miles driven = <<120-30=90>>90 more miles
He has 1.5 hours - 0.5 hours = <<1.5-0.5=1>>1 hour to drive the remaining distance
He must average 90 miles per hour to drive the remaining 90 miles in 1 hour
#### 90