Hey there! This one is super easy. We are solving for liters, which is volume, right? Whats an equation for volume of a cube? That's basically what a room is.
Volume of cube= width x length x height.
You are given all those measurements. The only thing you will need to work on here is converting ft^3 to L.
So first find volume in ft^3
Next convert ft^3 to inches^3 by using 1ft=12 inches conversion factor.
Convert inches^3 to cm^3, 1 inch= 2.54 cm.
Convert cm^3 to mL, 1cm^3 = 1 mL.
Then convert mL to L by using 1mL = 10^-3 L.
Also, when doing conversions, make sure to cube the conversion factors, since you are starting with ft^3.
So for example, if you have 10 ft^3, and you want to convert to inches: 10 ft^3 x (12 inch/ 1 ft) ^3
Let us know if you need further help with this. Good luck!