First she drives 2 hours * 60 mph = <<2*60=120>>120 miles
Then she drives 3 hours * 50 mph = <<3*50=150>>150 miles
The total miles driven is 120 + 150 = <<120+150=270>>270 miles
Jenna uses 270 / 30 = <<270/30=9>>9 gallons of gas.
The cost of gas is 9 * $2 = $<<9*2=18>>18
#### 18