You can solve this by using the equation (P1V1/T1) = (P2V2/T2). Plug in 0.50 atm for P1, leave V1 as the unknown, and plug in 325 K as T1. Then substitute 1.2 atm for P2, 48 L for V2, and 320 K for T2. Solve for V1, which is 117L, but since you round using two sig figs, your answer is C, 120 L. Hope this helps!
