There are
3 parts in this question:
1) To find the initial Boyle's constant

2) To find the final Boyle's constant

3) To verify whether gas is obeying Boyle's law or not
Given data:
The initial volume of the cylinder(in litres) =

= 12.0 L
The initial pressure(in atmospheric pressure) =

= 4.0 atm
The final pressure(in atmospheric pressure) =

= 8.0 atm
The final volume of the cylinder(in litres) =

= 6.0 L
First you need to know what
Boyle's law is:
<span>Boyle's law states that the
pressure of a given mass of an ideal gas is
inversely proportional to its
volume at a constant temperature.
</span>
The Mathematical form of Boyle's law is:

Where,
P = Pressure
V = Volume of the gas
k = Boyle's constant
Now let's solve aforementioned parts one by one:
1.
The initial volume of the cylinder(in litres) =

= 12.0 L
The initial pressure(in atmospheric pressure) =

= 4.0 atm
The Boyle's constant =

= ?
According to the Boyle's law,

=>

=

Plug-in the values in the above equation, you would get:

= 4.0 * 12.0 = 48
Ans-1)
= 482.
The final pressure(in atmospheric pressure) =

= 8.0 atm
The final volume of the cylinder(in litres) =

= 6.0 L
The Boyle's constant =

= ?
According to the Boyle's law,

=>

=

Plug-in the values in the above equation, you would get:

= 8.0 * 6.0 = 48
Ans-2)
= 48
3.
In order to verify Boyle's law, the initial Boyle's constant should be EQUAL to the final Boyle's constant, meaning:
= 
Since,

= 48

= 48
Therefore,
48=48.
Ans-3) Hence proved: The gas IS obeying the Boyle's law.
-i