Since the gas it is getting compressed with a change on temperature, we consider that the pressure is constant, and of course the number of mole is constant (same gas), therefore, from the ideal gas law
P
V
=
n
R
T
we can say:
V
T
=
constant
Therefore,
V
1
T
1
=
V
2
T
2
⇒
T
1
=
V
1
×
T
2
V
2
⇒
T
1
=
12
L
×
300
K
8
L
=
450
K
A=450k