Answer:
volume of empty space = 141.3 cm³
Step-by-step explanation:
volume of empty space = volume of the cylinder - volume of water
First, we need to calculate the volume of the container
volume of a cylinder = πr²h
  where r = radius of the container   and   h is the height of the container
r = 3cm  and h = 12 cm    π is a constant which is ≈ 3.14
volume of a cylinder = πr²h
                                   =3.14 × 3²×12
                                    =3.14×9×12
                                     =339.12 cm³
We will proceed to find the volume of water
since liquid will take the shape of its container,
then volume of water =  πr²h
r is the radius of the container   and    h is the height of the water
r = 3cm    and   h = 7cm      
 volume of water =  πr²h
                              = 3.14 ×3²×7
                               =3.14×9×7
                               =197.82 cm³
volume of empty space = volume of the cylinder - volume of water
                                           =339.12 cm³    -    197.82 cm³
                                           = 141.3 cm³
OR 
WE CAN SOLVE DIRECTLY
height of empty space = height of container - height of water
                                        = 12 - 7
                                         =5 cm
volume of empty space = πr²h
                                         =3.14×3²×5
                                         =3.14×9×5
                                          =141.3 cm³
volume of empty space = 141.3 cm³