Now we know: `(P_1\ \ V_1)/T_1=(P_2\ \ V_2)/T_2`
and we know Gay-Lussac's law `=` Volume constant
If we choose ONE for the value of `V`
NOTE: It doesn't really matter what value you choose they will cancel each other out being the same.
is the same as
This is Gay-Lussac's law