Hey there!
If you can paint a room that is 306 square feet with $72, you can divide $72 by 306 to see how much paint costs per square foot.
72 / 306 = about $0.24 per square foot
If you want, you can use the entire decimal of 0.23529412, but often times it doesn't matter which you use since you'll likely be rounding (especially with money problems) anyways.
So, multiply $0.24 by your new room size, 459 square feet, to get how much it will cost. It will cost $110.16 to paint this room.
Hope this helped you out! :-)