Answer: Joan can drive 111 more miles.
In total she can drive 330 miles with 15 gallons of gas.
If she already drove 219 miles, she has 111 more miles she can go before her gas runs out. (330-219 = 111) Joan can drive 111 more miles.
If you are also looking for how many gas she has left: 111 divided by 22 = 5 gallons (rounded) Joan has 5 gallons left.