Asample of ammonia gas at 75°c and 445 mm hg has a volume of 16.0 l. what volume will it occupy if the pressure rises to 1225 mm hg at constant temperature? 1 atm = 760 mm hg.

In this kind of exercises, you should  use the "ideal gas" rules: PV = nRT
P should be in Pascal: 
445mmHg = 59328Pa
1225mmHg = 163319Pa

V should be in cubic meter:
16L = 0.016 m3

R =  = constant
=
==> P1 * V1 = P2 * V2
V2 =  =
V2 = 0.00581 m3 = 5.81 L