Concept of is to be applied here.
Let the partial pressure of $Ar$ in the final mixture be $p_"Ar"$
Initially before mixing $ Ar$ had
Pressure $P_"Ar"=1.29$ atm
Temperature$T_"Ar"=223+273=500$ K
Volume $V_"Ar"=0.600$ L
In the mixture it acquires
Pressure $p_"Ar"=?$ atm
Temperature $T_"mAr"=23+227=250$ K
Volume $V_"mAr"=0.400$ L
So by combined Boyle's and Charles's equation for ideal gas we can write
$(p_"Ar"xxV_ "mAr")/T_"mAr"=(P_"Ar"xxV_"Ar")/T_"Ar"$
$=>p_"Ar"=(P_"Ar"xxV_"Ar")/T_"Ar"xxT_ "mAr"/V_"mAr"$
$=>p_"Ar"=(1.29xx0.600)/500xx250/0.400=0.9675$ atm
Again let the partial pressure of $O_2$ in the final mixture be $p_(O_2)$
Initially before mixing $ O_2$ had
Pressure $P_(O_2)=535$ torr $~~0.535$ atm
Temperature$T_(O_2)=106+273=379$ K
Volume $V_(O_2)=0.200$ L
In the mixture it acquires
Pressure $p_(O_2)=?$ atm
Temperature $T_(mO_2)=23+227=250$ K
Volume $V_(mO_2)=0.400$ L
So by combined Boyle's and Charles's equation for ideal gas we can write
$(p_(O_2)xxV_ (mO_2))/T_(mO_2)=(P_(O_2)xxV_(O_2))/T_(O_2)$
$=>p_(O_2)=(P_(O_2)xxV_(O_2))/T_(O_2)xxT_ (mO_2)/V_(mO_2)$
$=>p_(O_2)=(0.535xx0.200)/379xx250/0.400=0.1765$ atm
So total pressure in the flask
$P=p_"Ar"+p_(O_2)=0.9675+0.1765=1.144$ atm